Avionic Make Sample

AVIONICS MADE SIMPLE By Mouhamed Abdulla Jaroslav V. Svoboda Luis Rodrigues

Montréal, Québec, Canada

Copyright © 2005 by M. Abdulla

All rights reserved. No part of this work shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the author. No liability is assumed with respect to the use of the information contained herein. The information provided is on an “as is” basis. Although every effort and precaution has been taken in the preparation of this book, the author assumes no responsibility for errors or omissions. Nor is any liability assumed for damages resulting from the information contained herein.

ABOUT THE AUTHOR

Mouhamed Abdulla received the B.Eng. degree in Electrical Engineering in December-2002 from Concordia University, Montréal, Québec, Canada. Presently, he is on the verge of finishing his M.Eng. in Aerospace Engineering through the direct supervision of Dr. Luis Rodrigues ([email protected]) also at Concordia University. Mouhamed is currently employed at IBM Canada Ltd. as a Support Specialist for IBM/Lenovo products. He has professional affiliations, including, among others, IEEE, AIAA, and OIQ. His research interests include VLSI design, VLSI process technology, DSP, and Avionics. He can be reached at [email protected].

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To the most precious person of my life: To My Mother

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ACKNOWLEDGMENT

First and foremost, I would like to express my sincere gratitude and respect to the late Dr. Jaroslav V. Svoboda. He was my first contact to this exciting field, and a true mentor to the many students that he had over the years including myself. May his soul rest in peace and he will always be with us in our hearts and thoughts. I am also grateful to my supervisor Dr. Luis Rodrigues for his guidance, support and encouragement. I also like to thank Dr. Marius Paraschivoiu for giving me the chance to work on this project. Further, I would like to thank Professor Anwar Abilmouna for extremely insightful information on avionic system design that he acquired over the many years in industry. Last but not least, I would like to thank Ms. Leslie Hosein for always taking the time to answer my many questions on administrative issues and deadlines.

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PREFACE

The purpose of this book is to present aerospace electronic systems, also known as avionics, in a logical and comprehensible fashion. In fact, when we talk of avionics we usually refer to the following 20 acronyms:

ADF NDB VOR DME

TACAN VORTAC RNAV RMI / HSI

LORAN-C OMEGA INS / IRS DNS

GPS ALS VASIS ILS-LOC

ILS-GS0 MB MLS DGPS

These acronyms form the basics and fundamentals of avionics. Now you might ask yourself: what new is this work bringing? After all many authors with large amount of experience in the field have written books on the subject; many conference papers have tested and studied aspects of avionics; hundreds if not thousands of websites on the worldwide web have avionic related documents.

To answer the question above I need to mention that it is definitively true that information exist, and naturally I have used relevant information in this book from the above sources. However, most of the information sources available to the world, i.e. books, papers, and websites, come short in the following:

They don’t include all basic avionic systems in a single piece of work. Usually the reader must look at different locations to get the fundamentals of a system.

Even if by luck we come across a work that does include relevant information, it usually fails in organization, presentation, and optimization of the data.

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Many books are filled with so much information that as an example by the 20th page on a specific avionic hardware, we will completely forget the main purpose of the system. In other words, we would not even know what output is expected using that specific avionics. Most probably in such a scenario, the author either diverged to a different sidetopic or maybe he/she might have concentrated on a specific aspect of the system and forget the bigger picture.

Because of the reasons outlined above, among others, I decide to once and for all explain avionics in a systematic fashion with clear and concise terms. Consequently, this book should also be proven to be effective as a refresher on a particular technology. Say in five or even ten years from now, we could simply target the chapter and section of interest and obtain the fundamentals of a system in matter of minutes [fundamentals usually don’t change with time or maybe change with a slow rate; data on the other hand would most probably be outdated by then].

In is often said by professionals in the field of literature and language, that to teach someone [i.e. students] about something [i.e. basic avionics] one needs to use the method of questioning. In fact, this logical method is based on six interrogations also known as 5W+H:

WHAT: What is the purpose of this system? What is the useful output that I am getting after using this system?

WHO: Who is permitted to use this system? Civilian? Military? or Both?

WHERE: Where is this system located? On the ground? In the aircraft? In space?

HOW: How does this system work? What are the logical steps [block diagrams] in the operation of this system?

WHY: Why is this system good [advantages]? or Why is it bad [disadvantages]?

WHEN: When was this system certified as a liable avionic tool? What is the future of this system? Will it be phased-out? or Will it survive? And if so for how long? vi

I will try as much as possible to provide sufficient answers to these questions. In fact, the strategy and logic used to provide simple answers to the above interrogations are as follows:

I will first look for the answers from the class notes of our very own Concordia professor, the late Dr. Jarslov Svoboda. In case I don’t find the answers there or that I need a second opinion or that I am simply not sure of the integrity or validity of the of the data due to fast innovations of avionic technologies, I will refer to other sources as enumerated in the reference section of this book.

I am pleased and honored to have Dr. Luis Rodrigues as my supervisor for this work. His contribution consists mainly on reviewing the topics; provide constructive comments, and enforce the rules and regulations in regard to copyrights.

The book is written in point format approach without excessive details so that it is easy to read and memorize. As for the layout of the information, it is presented in an organized and an optimized fashion. In the sense that if different systems with similar purpose are explained, then a symmetrical structure will be outlined to simplify the comparison study among technologies.

Moreover, a major emphasis is given to the illustrations and diagrams to facilitate the understanding of the material. Most of the diagrams were illustrated using Visio Professional 5.0 available from Visio Corporation. To be more specific, the illustrations used throughout this book are classified into 7 types:

Illustrations created fully with Visio using my personal understanding of a topic.

Illustrations that I have seen in class notes, and then reproduced exactly the same thing using Visio.

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Illustrations that I have seen in class notes, and then modified it using Visio. Usually when I recreate a figure that I have seen in a related source [class notes or websites], I will modify it by either making it simple or even more complex so that it becomes complete yet easy to understand.

Illustrations that I have seen in class notes, and then recreated fully the same thing using Visio, with modifications to reflect my perception of the subject.

Illustrations found on the worldwide web available to the general public.

Illustrations that I have seen on the worldwide web, and then modified it using Visio.

Illustrations that I have seen on the worldwide web, and then recreated fully the same thing using Visio, with modifications.

Also, on occasions, a programming code is used to facilitate quick calculation for a specific transformation. The code will be based on the Matlab programming language available from MathWorks Inc.

As far as the content is concerned, it is partitioned into two major sections: Preliminary and Avionics. The Preliminary section does not discuss avionic systems; it is there to assist the reader on general aerospace facts that could be useful once the avionic section is reached. The 20 acronyms listed above would be explained in the Avionics section, which in principle forms the essence of this book. Now since the major theme of this work is efficiency, then naturally we should deduce that avionic systems would not be discussed equally. In other words, systems that have retired or that are on the verge of being phased-out will be discussed briefly; where as systems that are important today and have promising improvement for the future will be explained in-depth.

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Finally, readers should realize that the work was prepared to be self-contained, such that no references or prerequisites are required or assumed to understand the principal of a given technology. In fact, all type of readers coming from different professional background should normally understand the topics effortlessly. Obviously, some may choose to thrive more in a specific subject which then would be quite normal to reference specialized and advanced literatures.

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ACRONYMS Numbers

2D 3D

A

A ABS A/C ADC ADF ADIZ AFIS AGL AI AKA A/L ALS ALT AM ARINC ARSA ARTCC ASRA ATA ATC ATCTC

C

D

Latitude and Longitude Latitude, Longitude, and Altitude Alert Area Automatic Breaking System Aircraft Air Data Computer Automatic Direction Finder Air Defense Identification Zone Airborne Flight Information System Above Ground Level Airspeed Indicator Also Known As Approach Landing Approach Lighting System Altitude Amplitude Modulation Aeronautical Radio Inc. Airport Radar Service Area Air Route Traffic Control Center Aviation Safety Reporting System Airport Traffic Area Air Traffic Control Air Traffic Control Tower Center

C C/A CAS

Center Course Acquisition Modulation Calibrated Airspeed

CAT CDI CG CIV Cs

Category

DA DB DG DGPS DH DME DNS DoD DoT DR

DSARC Defense System Acquisition and Review Council Daylight Saving Time DST E

E EAS ECEF EFIS EHF ELF ELT EM EMI ETA EU

F

FAA FAF F/C FCC FL FM FMS FREQ FSS

G

Course Deviation Indicator Center of Gravity Civilian Cesium Drift Angle Database Directional Gyroscope Differential Global Positioning System Decision Height Distance Measuring Equipment Doppler Navigation System Department of Defense Department of Transportation Dead Reckoning

East Equivalent Airspeed Earth Centered Earth Fixed Electronic Flight Instrument System Extremely High Frequency Extremely Low Frequency Emergency Locator Transmitter Electromagnetic Electromagnetic Interference Estimated Time of Arrival European Union Federal Aviation Administration Final Approach Fix Flight Compartment Federal Communications Commission or Flight Control Computer Flight Level Frequency Modulation Flight Management System Frequency Flight Service Station

GLONASS Global Navigation Satellite System GMT Greenwich Mean Time GND Ground Global Positioning System GPS Ground Speed GS GS0

Glideslope

H

HDG HF HSI HUD HW

Heading High Frequency Horizontal Situation Indicator Heads Up Display Hardware

I

IAF IAP IAS IATA ICAO ICAT

Initial Approach Fix Instrument Approach Procedures Indicated Airspeed International Air Transport Association International Civil Aviation Organization International Center for Air Transportation

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Identification ID IFATCA International Federation of Air Traffic Controller Associations Instrument Flight Rules IFR Instrument Landing System ILS Inner Marker IM Inertial Navigation System INS Inertial Reference System IRS International Telecommunication Union ITU K L

M

N

O

KTS

Marker Beacon Minimum Descent Altitude Medium Frequency Military Massachusetts Institute of Technology Microwave Landing System Middle Marker Military Operations Area Mean Sea Level Military Training Route

P PCA PED P/O PRC P(Y)

Prohibited Area Positive Control Area Portable Electronic Device Phased Out Pseudo Random Code Precise Encrypted Modulation

Q

QFE QNE QNH

Pressure at Field Elevation Pressure at Standard Sea Level Pressure at Nautical Height

R

R RA RAPCON RATCC Rb R&D RMI RNAV RPS RVR Rx

Restricted Area or Right Radio Altimeter Radar Approach Control Facility Radar Air Traffic Control Center Rubidium Research and Development Radio Magnetic Indicator Random or Area Navigation Revolutions Per Second Runway Visibility Range Receiver

S

S SA SAT SATCOM SHF SLF SM SVN

South Selective Availability Satellite Satellite Communications Super High Frequency Super Low Frequency Statue Miles Satellite Vehicle Number

T

TACAN TAS TCA TCAS TCCA TDP TK TRACON Tx

Tactical Air Navigation System True Airspeed Terminal Control Area Traffic Alert and Collision Avoidance System Transport Canada Civil Aviation Touchdown Point Track Terminal Radar Approach Control Transmitter

U

UHF ULF US USAFSC

Ultra High Frequency Ultra Low Frequency United States of America US Air Force Space Command

North N NASA National Aeronautics and Space Administration NAV Navigation NAVAID Navigational Aid NAVSTAR Navigation System with Timing And Ranging Non Directional Beacon NDB NiCd Nickel Cadmium Nickel Hydrogen NiH2 Nautical Miles NM Outer Marker OM OMEGA Optimized Method for Estimated Guidance Accuracy

Outer-Space

P

Knots

Left L LAAS Local Area Augmentation System Latitude LAT Liquid Crystal Display LCD Low Frequency LF LOC Localizer LON Longitude Line of Position LOP LORAN-C Long Range Navigation (revision-C) Line of Sight LOS Local Standard Time LST MB MDA MF MIL MIT MLS MM MOA MSL MTR

OS

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USNO V

VASIS VFR VHF VLF VOR VORTAC VSI

W

W WA WAAS WGS-84 WMS WPT WRT WS WXR

US Naval Observatory Visual Approach Slope Indicator System Visual Flight Rules Very High Frequency Very Low Frequency VHF Omni-directional Range VOR & TACAN Vertical Speed Indicator Warning Area or West Wind Angle Wide Area Augmentation System World Geodetic System of 1984 WAAS Master Station Waypoint With Respect To Wind Speed Weather Radar System

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TABLE OF CONTENTS

Part I – Preliminary Chapter 1 – Introduction ................................................................................................................................. 2 1.1 Air Navigation .......................................................................................................................................... 3 1.2 NAV Methods........................................................................................................................................... 3 1.3 History of Air NAV .................................................................................................................................. 4

Chapter 2 – Basic Concepts ............................................................................................................................. 8 2.1 Earth Coordinate Systems......................................................................................................................... 9 2.2 Earth Mapping Systems .......................................................................................................................... 13 2.3 International NAV Standards.................................................................................................................. 14 2.4 Airspace Structure................................................................................................................................... 15 2.5 Air Traffic Control System ..................................................................................................................... 18 2.5.1 Visual Flight Rule – VFR ................................................................................................................ 19 2.5.2 Instrument Flight Rule – IFR........................................................................................................... 20 2.5.3 VFR and IFR.................................................................................................................................... 23

Chapter 3 – Early NAV .................................................................................................................................. 24 3.1 Flight Controls ........................................................................................................................................ 25 3.2 Basics of Flight Instruments ................................................................................................................... 27 3.2.1 Pitot Static Instruments .................................................................................................................... 27 3.2.2 Attitude Instruments......................................................................................................................... 32 3.2.3 HDG Instruments ............................................................................................................................. 33 3.3 Pilotage and Dead Reckoning................................................................................................................. 35

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Chapter 4 – Air Communication ................................................................................................................... 41 4.1 Radio Wave Propagation ........................................................................................................................ 42 4.1.1 GND Wave....................................................................................................................................... 42 4.1.2 Sky Wave ......................................................................................................................................... 44 4.1.3 LOS Wave........................................................................................................................................ 45 4.2 Communications ..................................................................................................................................... 47

Part II – Avionics Chapter 5 – Short-Range NAVAIDS ............................................................................................................ 50 5.1 Automatic Direction Finder – ADF ........................................................................................................ 51 5.2 VHF Omni-directional Range – VOR .................................................................................................... 54 5.3 Distance Measuring Equipment – DME ................................................................................................. 59 5.4 Tactical Air Navigation – TACAN......................................................................................................... 63 5.5 VOR and TACAN – VORTAC .............................................................................................................. 64 5.6 Random or Area Navigation – RNAV.................................................................................................... 66 5.7 Combined Displays................................................................................................................................. 68 5.7.1 Radio Magnetic Indicator – RMI..................................................................................................... 68 5.7.2 Horizontal Situation Indicator – HSI ............................................................................................... 68

Chapter 6 – Long-Range NAVAIDS ............................................................................................................. 70 6.1 Long Range Navigation (revision-C) – LORAN-C................................................................................ 71 6.2 Optimized Method for Estimated Guidance Accuracy – OMEGA ........................................................ 73 6.3 Inertial Navigation System or Inertial Reference System – INS or IRS................................................. 76 6.4 Doppler Navigation System – DNS........................................................................................................ 81 6.5 Global Positioning System – GPS .......................................................................................................... 83

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Chapter 7 – Approach-Landing NAVAIDS ............................................................................................... 100 7.1 Basics of Approach-Landing – A/L...................................................................................................... 101 7.2 Instrument Landing System – ILS ........................................................................................................ 106 7.3 Microwave Landing System – MLS ..................................................................................................... 111 7.4 Differential Global Positioning System – DGPS.................................................................................. 114

Chapter 8 – Summary .................................................................................................................................. 119 8.1 Nomenclature........................................................................................................................................ 120 8.2 Summary of Avionic Systems .............................................................................................................. 120 8.3 Avionic Receivers and/or Transmitters ................................................................................................ 122 8.4 Airborne Antennas ................................................................................................................................ 122

Appendices

Appendix A: Matlab Code {hh,mm,ss} ĺ {decimal} ................................................................................ 124 Appendix B: Matlab Code {hh,mm,ss} ĸ {decimal}................................................................................. 125 Appendix C: Relations between {ALT,Temperature,Pressure} ļ{Atmosphere}.................................. 127 Appendix D: Matlab Code {X,Y,Z} ĺ {LAT,LON,ALT} ........................................................................ 130 Appendix E: Matlab Code {X,Y,Z} ĸ {LAT,LON,ALT}......................................................................... 131 Appendix F: GPS SATs launched from February-1978 until November–2005...................................... 132 Appendix G: Effect of Portable Electronic Devices on Airborne Avionics ............................................. 134 Appendix H: Morse code.............................................................................................................................. 136 Appendix I: Aerospace in Québec ............................................................................................................... 137 Appendix J: Avionic Related Courses in Québec Universities ................................................................. 138

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References A – Books ....................................................................................................................................................... 140 B – Class Notes .............................................................................................................................................. 140 C – Papers...................................................................................................................................................... 141 D – Aerospace Search Tools......................................................................................................................... 143 E – Learning Aids ......................................................................................................................................... 143 F – GPS .......................................................................................................................................................... 144 G – GLONASS .............................................................................................................................................. 144 H – GALILEO............................................................................................................................................... 144 I – Chart Symbols ......................................................................................................................................... 145 J – Miscellaneous........................................................................................................................................... 145 K – Illustrations............................................................................................................................................. 145

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LIST OF ILLUSTRATIONS

Figure-1.1 GS estimation ......................................................................................................................... 3 Figure-1.2 Radar system .......................................................................................................................... 5 Figure-1.3 SAT system with an integrated transponder .......................................................................... 5 Figure-2.1 Earth coordinate system left:[K4-1]....................................................................................... 9 Figure-2.2 Sign convention used for a 2D mapping of the earth surface ................................................ 9 Figure-2.3 Great circle [K6-1] ............................................................................................................... 10 Figure-2.4 Rhumb line [K3-1] ............................................................................................................... 11 Figure-2.5 GMT standard [K3-2] .......................................................................................................... 12 Figure-2.6 Lambert conic projection [K6-2] ......................................................................................... 13 Figure-2.7 Transverse Mercator projection [K6-2] ............................................................................... 13 Figure-2.8 Logo of national and international bodies............................................................................ 14 Figure-2.9 Airspace structure for Canada and the US as of 1991 [K6-3].............................................. 15 Figure-2.10 Airspace summary [K6-3].................................................................................................. 17 Figure-2.11 V- or J-Airway NAV (i.e. without using waypoints)......................................................... 18 Figure-2.12 VFR weather minima for Canada and the US [K3-3]........................................................ 20 Figure-2.13 Radar method enables small separation distances ............................................................. 21 Figure-2.14 IFR flight phases [K3-4] .................................................................................................... 21 Figure-2.15 Holding fix method and ILS for the landing phase [K3-5]................................................ 22 Figure-2.16 VFR and IFR cruising ALTs [K6-4].................................................................................. 23 Figure-3.1 A/C control surfaces [K1-1]................................................................................................. 25 Figure-3.2 A/C 6-degrees of freedom [K2-1] ........................................................................................ 25 Figure-3.3 Controlling A/C 6-degrees of freedom ................................................................................ 26

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Figure-3.4 Basic flight instruments [K6-5]............................................................................................ 27 Figure-3.5 Pitot static instrument system [K3-6]................................................................................... 28 Figure-3.6 Height versus pressure or density ........................................................................................ 30 Figure-3.7 Static pressure variation with vertical motion...................................................................... 32 Figure-3.8 Rate of turn of the A/C......................................................................................................... 32 Figure-3.9 Turn and bank indicator [K6-6] ........................................................................................... 33 Figure-3.10 Directional gyroscope indicator [K6-7] ............................................................................. 33 Figure-3.11 Earth Magnetic field [K6-8]............................................................................................... 34 Figure-3.12 Compass deviation error [K3-7]......................................................................................... 35 Figure-3.13 Definition of speed vectors ................................................................................................ 35 Figure-3.14 Distinction between Required TK and TK Made Good [K3-8]......................................... 36 Figure-3.15 100 Drift Lines [K3-9]........................................................................................................ 36 Figure-3.16 Double TK Error Method [K3-10]..................................................................................... 37 Figure-3.17 Visual TK Alteration Method [K3-10] .............................................................................. 37 Figure-3.18 Two Point Visual Range Method....................................................................................... 38 Figure-3.19 Opening/Closing Angles Method [K3-11]......................................................................... 38 Figure-3.20 Return to Point of Departure Method................................................................................. 39 Figure-3.21 Triangulation Method [K1-2]............................................................................................. 39 Figure-4.1 GND and sky wave propagation [K6-9] .............................................................................. 42 Figure-4.2 Frequency band classification [K6-10] ................................................................................ 43 Figure-4.3 GND wave signal attenuation [K3-12] ................................................................................ 43 Figure-4.4 Received signal power versus “L” [K1-3] ........................................................................... 44 Figure-4.5 Frequency bandwidth for GND, sky, and LOS waves......................................................... 45 Figure-4.6 Graphical definition of “L” .................................................................................................. 45 Figure-4.7 Maximum LOS range due to earth curvature [K6-11]......................................................... 46

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Figure-4.8 LOS wave signal attenuation [K3-12].................................................................................. 46 Figure-4.9 LOS wave signal attenuation due to atmospheric conditions [K1-4] .................................. 46 Figure-4.10 AM and FM modulation techniques [K6-12] .................................................................... 47 Figure-4.11 Noise canceling headset [K4-2] ......................................................................................... 48 Figure-5.1 Examples illustrating the ADF principle [K6-13]................................................................ 51 Figure-5.2 Wrong station homing [K6-13]............................................................................................ 51 Figure-5.3 Correct station homing [K6-13] ........................................................................................... 52 Figure-5.4 NDB GND station [K4-3] .................................................................................................... 53 Figure-5.5 ADF–Rx system [K3-13] ..................................................................................................... 53 Figure-5.6 Examples illustrating the VOR principle [K6-14] ............................................................... 55 Figure-5.7 VOR does not provide A/C HDG; it only gives the radial occupied by the A/C ................ 55 Figure-5.8 VOR GND station [K4-4] .................................................................................................... 56 Figure-5.9 VOR–Tx system [K3-14]..................................................................................................... 57 Figure-5.10 VOR–Rx system [K3-15]................................................................................................... 57 Figure-5.11 CDI [K6-15] ....................................................................................................................... 57 Figure-5.12 Examples of signals observed by the VOR-Rx at different radials [K3-16]...................... 58 Figure-5.13 Example illustrating the DME principle ............................................................................ 59 Figure-5.14 DME GND station left:[K3-17] right:[K4-5]..................................................................... 60 Figure-5.15 VOR-DME GND station left:[K4-6] right:[K5-1]............................................................. 60 Figure-5.16 DME airborne system [K3-17]........................................................................................... 61 Figure-5.17 DME slant error.................................................................................................................. 62 Figure-5.18 Greatest DME slant error ................................................................................................... 62 Figure-5.19 TACAN GND station [K4-7]............................................................................................. 63 Figure-5.20 VORTAC GND station left:[K4-8] right:[K3-18] ............................................................. 65 Figure-5.21 Example illustrating the RNAV principle using VORTAC GND stations [K6-16].......... 66

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Figure-5.22 RNAV airborne system ...................................................................................................... 67 Figure-5.23 RMI left:[K5-2].................................................................................................................. 68 Figure-5.24 HSI [K5-3] ......................................................................................................................... 69 Figure-6.1 Formation of the hyperbolic grid [K6-17] ........................................................................... 71 Figure-6.2 Position fix using LORAN-C system [K6-18]..................................................................... 71 Figure-6.3 LORAN-C GND stations left:[K4-9]................................................................................... 72 Figure-6.4 LORAN-C airborne processor ............................................................................................. 73 Figure-6.5 Time-frequency transmission scheme for OMEGA GND stations [K6-19]........................ 74 Figure-6.6 Location of the OMEGA GND Tx stations [K6-19] ........................................................... 75 Figure-6.7 Airborne INS interfaces ....................................................................................................... 76 Figure-6.8 Stable-platform INS left:[K4-10]......................................................................................... 77 Figure-6.9 2D-view of a stable-platform INS [K3-19].......................................................................... 77 Figure-6.10 3D-view of a stable-platform INS [K3-20]........................................................................ 77 Figure-6.11 Laser gyroscope used by the strap-down INS left:[K4-10] right:[K6-20]......................... 78 Figure-6.12 Computation sequence in stable-platform and strap-down INS ........................................ 80 Figure-6.13 DNS.................................................................................................................................... 81 Figure-6.14 Example illustrating calculation of GS using DNS provided A/C is flying straight ......... 81 Figure-6.15 General tradeoff that exists between NAVAID systems.................................................... 83 Figure-6.16 A/C position fix using GPS [K6-21].................................................................................. 87 Figure-6.17 Graphical definition of {X,Y,Z} and {LAT,LON,ALT} [K6-22]..................................... 89 Figure-6.18 GPS GND facilities ............................................................................................................ 90 Figure-6.19 Tabular location of GPS GND stations.............................................................................. 90 Figure-6.20 Location of GPS GND stations [K6-23] ............................................................................ 91 Figure-6.21 GPS frequencies [K6-24] ................................................................................................... 92 Figure-6.22 Number of operational SATs and active Clocks w.r.t. GPS generations........................... 93

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Figure-6.23 Coverage angle of GPS SATs [K3-22] .............................................................................. 93 Figure-6.24 GPS generations [K5-4] ..................................................................................................... 94 Figure-6.25 GPS SAT Constellation left:[K6-25] right:[K6-26]........................................................... 95 Figure-6.26 GPS-Rx [K3-23]................................................................................................................. 96 Figure-6.27 Typical GPS errors [K3-24] ............................................................................................... 97 Figure-6.28 GPS error sources [K6-27]................................................................................................. 97 Figure-6.29 GALILEO, GPS, and GLONASS SAT ALTs ................................................................... 99 Figure-7.1 A/L phases [K3-25]............................................................................................................ 101 Figure-7.2 MDA/DH decision tree ...................................................................................................... 102 Figure-7.3 ICAO DH values for IFR precision approaches [K6-28]................................................... 102 Figure-7.4 ALS [K3-26] ...................................................................................................................... 103 Figure-7.5 VASIS [K6-29] .................................................................................................................. 104 Figure-7.6 Runway Numbering [K6-30] ............................................................................................. 105 Figure-7.7 ILS [K3-27]........................................................................................................................ 106 Figure-7.8 ILS CAT-II runway [K3-26].............................................................................................. 106 Figure-7.9 ILS-LOC [K6-31]............................................................................................................... 107 Figure-7.10 ILS-GS0 [K6-31] .............................................................................................................. 108 Figure-7.11 LOC, GS0, and MB-Txs [K5-5] ....................................................................................... 109 Figure-7.12 Transmissometer [K4-11] ................................................................................................ 109 Figure-7.13 LOC/GS0-Rx [K3-28] ...................................................................................................... 110 Figure-7.14 MB-Rx and its alerts left:[K3-29] right:[K6-28] ............................................................. 110 Figure-7.15 Terrain effect in ILS [K3-30]........................................................................................... 111 Figure-7.16 MLS [K6-32].................................................................................................................... 112 Figure-7.17 Configuration of MLS GND systems [K6-33]................................................................. 113 Figure-7.18 Azimuth and Elevation-Txs [K5-6] ................................................................................. 113

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Figure-7.19 DGPS [K4-12].................................................................................................................. 114 Figure-7.20 DGPS used to correct A/C position fix [K6-34] .............................................................. 115 Figure-7.21 Typical DGPS errors [K3-31] .......................................................................................... 116 Figure-7.22 DGPS error sources [K6-27]............................................................................................ 117 Figure-8.1 Short-Range Avionics ........................................................................................................ 120 Figure-8.2 Long-Range Avionics ........................................................................................................ 121 Figure-8.3 A/L Avionics...................................................................................................................... 121 Figure-8.4 Avionic Rxs and/or Txs ..................................................................................................... 122 Figure-8.5 Color coding used to classify avionics............................................................................... 122 Figure-8.6 Top-view of airborne avionics [K2-2] ............................................................................... 123 Figure-8.7 Bottom-view of airborne avionics [K2-2].......................................................................... 123 Figure-C.1 Atmosphere layers [K5-7] ................................................................................................. 127 Figure-C.2 ALT as a function of temperature [K5-8].......................................................................... 128 Figure-C.3 ALT as a function of pressure [K5-9] ............................................................................... 129 Figure-F.1 GPS Blocks-I, II and IIA [K6-26]...................................................................................... 132 Figure-F.2 GPS Blocks-IIR and IIR-M [K6-26].................................................................................. 133 Figure-G.1 Percentage of PEDs interfering with avionic systems ...................................................... 134 Figure-G.2 Percentage of a specific PED interfering with a specific avionic system ......................... 135 Figure-G.3 Flight phases associated with incidences .......................................................................... 135 Figure-H.1 Morse code [K6-35] .......................................................................................................... 136 Figure-I.1 Aerospace in North American cities [K4-13] ..................................................................... 137

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Part I Preliminary

1

Chapter 1 Introduction

There is much pleasure to be gained from useless knowledge. — Bertrand Russell

2

Chapter 1: Introduction

M. Abdulla

1.1 Air Navigation Air Navigation (NAV) is the process of directing the movement of an aircraft (A/C) from one point to the other. It involves the control of position, direction, and speed of an A/C with respect to time.

1.2 NAV Methods •

Pilotage: Early method of NAV based on visual reference to landmarks.

•

Dead Reckoning (DR): NAV by extrapolating. That is, determining the present position through the knowledge of a previous reference position. 1) 2)

Obtain an estimate of the Ground Speed (GS). Integrate over-time to obtain the position.

x = ³ GS (t ) dt

(1.1)

North

TK

TAS

HD G nd Wi

TAS: HDG: GS: TK:

True Airspeed Heading Angle Ground Speed Track Angle

WS: WA: δ:

Wind Speed Wind Angle Drift Angle

W

A

δ

GS

WS Figure-1.1 GS estimation

→

GS = {GS ∠TK } =

→

TAS + {TAS ∠HDG } +

3

→

WS {WS ∠WA }

(1.2)

Chapter 1: Introduction

M. Abdulla

•

Radio NAV: NAV through the use of wireless communication signals broadcasted by Ground (GND) or A/C based radio station.

•

Celestial NAV: NAV in reference to heavily bodies, such as: sun, moon, planets, stars, etc.

•

Inertial NAV: NAV based on double integrating the A/C acceleration measured using airborne equipments.

x = ³³ a (t ) dt 1dt 2 •

(1.3)

Satellite NAV: NAV through the use of data broadcasted by a Satellite (SAT) based transmitter.

1.3 History of Air NAV •

1910’s (WWI): 1) 2) 3) 4) 5) 6)

•

Compass Altimeter: Instrument to measure height above a reference. Airspeed Indicator Watch Pilotage DR

1920’s: 1) Blind Flying: i.e. without looking from the cockpit window. 2) Directional Gyroscope: Instrument that sense angular motion using momentum of a spinning mass with respect to (w.r.t) 1 or 2-axes orthogonal to the spin axis. 3) Artificial Horizon: Gyro operated flight instrument that shows the inclination of an A/C w.r.t. a horizon bar. 4) Advanced DR

•

1930’s: 1) 2) 3) 4)

Basic-T: Standardization of flight instruments. Electronic NAV Radio Communication Autopilot

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Chapter 1: Introduction •

M. Abdulla

1940’s (WWII): 1) Celestial NAV: Progress in long-range NAV. 2) Radio Communication 3) Radar: System that uses radio waves for detecting and locating objects in space. ™Turn on radar Transmitter (Tx). ™Radar sends a radio wave beam to the object. ™Turn off radar Tx and turn on its Receiver (Rx). ™Radar detects the echo reflected by the object. ™Time for the traveled beam from the object to the radar is captured as well as the Doppler shift of the echo. ™Since radio wave travel with the speed of light c, hence position is known; and the speed of the object is also known through the Doppler shift data. Tx / Rx Radar

Beam Object

Reflect

Figure-1.2 Radar system

x =c t 4) Transponder: Communication system that has a combined Tx and Rx. Used in A/C and SATs for 2-way communications. Satellite with Transponder

B

A

Figure-1.3 SAT system with an integrated transponder

5

(1.4)

Chapter 1: Introduction •

M. Abdulla

1950’s & 60’s: 1) Jet-Age 2) Avionics: New term meaning electronic NAV was standardized. 3) Avionic Systems: Progress in electronic air NAV. ™Automatic Direction Finder (ADF): System that tells us where the A/C is located. ™Very High Frequency (VHF) Omni-directional Range (VOR): System that tells us the A/C angle1 w.r.t to a GND station. ™Tactical Air Navigation System (TACAN): Military (MIL) system used to provide bearing and distance between the A/C and a GND station. ™Integrated VOR & TACAN system (VORTAC): GND station with VOR and TACAN antennas. ™Instrument Landing System (ILS): System that guides the A/C for an ideal landing. ™Inertial Navigation System (INS): Airborne system that gives continuous A/C position information through DR. 4) Sophisticated Autopilot System

•

Today: 1) Space-Age 2) Integrated Flight Control 3) Flight Management System (FMS): System that can fly the A/C. 4) Electronic Flight Instrument System (EFIS): Touch-operated screen showing all flight and engine instruments required to fly an A/C with audio capabilities. 5) Heads-Up Display (HUD): Cockpit window will display navigational information, therefore no need to incline to observe data on dashboard but rather look straight to the window.

1

Angle information or bearing or azimuth are similar terms and could be used interchangeably.

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Chapter 1: Introduction

M. Abdulla

6) Microwave Landing System (MLS): MIL system that does not require a straight flight path in order to land. 7) Long Range Navigation (LORAN-C): System used to determine A/C position. 8) Optimized Method for Estimated Guidance Accuracy (OMEGA): System used to determine A/C position. 9) Global Positioning System (GPS): System used to determine A/C position using SATs. 10) Air Traffic Control (ATC): Promoting safety an order in airspace. 11) Free-Flight Concept: The idea is based on letting every airplane in sky to know of each other so as to increase traffic awareness, avoid collisions, and reduce ATC workload.

7

Chapter 2 Basic Concepts

Knowledge will forever govern ignorance: And a people who mean to be their own Governors, must arm themselves with the power which only knowledge gives. — James Madison

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Chapter 2: Basic Concepts

M. Abdulla

2.1 Earth Coordinate Systems •

Latitude / Longitude: Location of any point on earth is defined by its Latitude (LAT) and Longitude (LON) coordinates.

90D

North

↑ 0D

LAT:

Equator

↓ 90D

South D

LON: 180 ← West

0D → 180

meridian

D

East

Figure-2.1 Earth coordinate system left:[K4-1]

N (+)

{LAT , LON} + 900

LAT

W (-)

E (+) LON

- 900 - 1800

+ 1800

S (-) Figure-2.2 Sign convention used for a 2D mapping of the earth surface

1) Transformation from hour/minute/second to decimal format2: ­° ( ( seconds 60 ) + minutes ) ½° decimal = ± ® + hours ¾ 60 °¯ °¿ 2

(2.1)

The ± in the formula is assigned as per the sign convention of Figure-2.2. A Matlab code for this transformation is available in Appendix A.

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Chapter 2: Basic Concepts

M. Abdulla

2) Transformation from decimal to hour/minute/second format3: a = decimal hours = integer ( a ) = i.e. take only the integer part of a b = ( a − hours ) × 60

(2.2)

minutes = integer ( b ) = i.e. take only the integer part of b seconds = ( b − minutes ) × 60

Montréal / Québec / Canada ­ LAT : 450 30′ = 45.50 = +45.50 ½° ° North North ® ¾ 0 0 = −73.5830 ° °¯ LON : 73West35′ = 73.583 West ¿

•

Great Circle: This surface line is used in long-distance-flying. It is based on the intersection of a sphere and a plane through its center. In other words, to obtain the shortest distance between any 2 points on the earth surface, we must have a plane that cuts these 2 points and the earth center.

Earth Center C B A Great Circle

Figure-2.3 Great circle [K6-1]

§ Rπ · -1 D=¨ ¸ cos {sin ( LAT1 ) sin ( LAT2 ) + cos ( LAT1 ) cos ( LAT2 ) cos ( LON1 − LON 2 )} © 180 ¹ = (111.320 ) cos-1 {sin ( LAT1 ) sin ( LAT2 ) + cos ( LAT1 ) cos ( LAT2 ) cos ( LON1 − LON 2 )}

3

(2.3)

North/South or East/West is assigned as per the direction convention of Figure-2.2. A Matlab code for this transformation is available in Appendix B.

10

Chapter 2: Basic Concepts

R: D:

M. Abdulla

Earth radius [ 6,378.137 km ] . Shortest distance between 2 points on the earth surface [ km ] .

LAT1 : Latitude of the 1st point on the earth surface [ degrees ] . LAT2 : Latitude of the 2nd point on the earth surface [ degrees ]. LON1 : Longitude of the 1st point on the earth surface [ degrees ] .

LON 2 : Longitude of the 2nd point on the earth surface [ degrees ].

•

Rhumb Line: This surface line is used in short-distance-flying. It is based on traveling between 2 points by intersecting the meridian at a constant angle.

Meridian

N

Angle

W

E

S

Figure-2.4 Rhumb line [K3-1]

•

Time: Earth is divided into 24 time zones.

1:

Earth speed = 1 revolution / 24 hrs

­1 revolution = 360D → 24 hrs ½ 2: ® ¾ → 1 hr ¿ χ ¯ 3: 15D LON ≡ 1 hr

Ÿ χ = 15D

(2.4)

1) Daylight Saving Time (DST): During the summer, zonetime is set forward by 1 hour.

™Not all countries observe DST. ™Even if countries use DST, some cities or provinces4 within that country will not take into consideration DST. 4

As an example, Canada uses the DST during summer; however the province of Saskatchewan does not.

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™The interpretation of summer differs from one nation to the other; and therefore, the beginning and end dates of DST is non-standardized and hence, varies from one country to the other. ™Some countries may decide to change5 the beginning and end dates of DST for various reasons. ™Every now and then some countries decide to implement the DST system. On the other hand, other nations that previously had DST may suddenly stop using it. 2) Local Standard Time (LST): It is the local time in a specific geographical area. 3) Greenwich Mean Time (GMT): Universal standard time is referred to as GMT6, Zulu or Z time. It is extremely important to realize that GMT never changes and DST has no effect whatsoever on GMT. Because of this important characteristic, GMT is mainly used in aviation as a time reference all across the world.

Slice London / UK Azores / Portugal Fernando de Noronha / Pernambuco / Brazil Nuuk / Greenland / Denmark

30°W

45°W

0°

°

15 W

15° E

30° E Athens / Greece

−1 0 +1 +2 −2 4.167%

4.167%

−3

4.167%

60° E Abu Dhabi / UAE

+3

4.167%

4.167%

60 W

Halifax / NS / Canada

45° E Baghdad / Iraq

4.167%

4.167%

°

Paris / France

+4 −4 75 E Islamabad / Pakistan Montréal / QC / Canada 75 W −5 Greenwich Mean Time +5 (GMT) +6 90 E Dhaka / Bangladesh Winnipeg / MA / Canada 90 W −6 Zone Time = GMT + Slice −7 ¡ : without taking into account DST +7 105 E Bangkok / Thailand Edmonton / AB / Canada 105°W −8 +8 ° Vancouver / BC / Canada 120 W 120 E Beijing / China +9 −9 4.167%

4.167%

°

°

4.167%

4.167%

°

¡

4.167%

4.167%

−10

150°W

+10 4.3%

4.167%

Honolulu / Hawaii / US

°

4.2%

4.167%

135°W

°

4.2%

4.167%

Anchorage/ Alaska / US

°

4.167%

4.167%

−11 ±12 +11 4.167%

4.3%

°

Apia / Samoa 165 W

180° E

4.3%

135° E Tokyo / Japan

150° E °

165 E

Sydney / New South Wales / Australia

Honiara / Solomon Islands

Wellington / New Zealand

Figure-2.5 GMT standard [K3-2] 5

As an example, the Energy Policy Act of 2005 signed by US President George W. Bush will extend DST by 4 weeks stating March-11-2007. The provincial governments of Québec and Ontario have decided to adapt this change as of 2007 in order to remain in synch with neighboring US. 6 GMT can be observed on: http://wwp.greenwichmeantime.com

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Chapter 2: Basic Concepts •

M. Abdulla

Nautical Mile (nm) / Knots (kts): 1:

Earth Radius = r Earth Circonference = 2π r

= 6,378.137 km = 40, 075.017 km

­360D = ( 360 deg )( 60 min/deg ) = 21, 600 min → 40, 075.017 km ½ 2: ® ¾ Ÿ χ = 1.852 km χ 1 min → ¯ ¿ = 1.852 km 1 minute = 1 nm 3: 1 knot = 1 nm/hr = 1.852 km/hr

(2.5)

2.2 Earth Mapping Systems Projection methods are used to represent the 3D spherical earth on a 2D flat surface. •

Lambert Conic Projection: This projection method is used in long-distance-flying. The meridians are straight lines that converge to the pole. Whereas the parallels are concave curves. Also, the scale is uniform throughout the map.

Figure-2.6 Lambert conic projection [K6-2]

•

Transverse Mercator Projection: This projection method is used in short-distance-flying.

Figure-2.7 Transverse Mercator projection [K6-2]

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Chapter 2: Basic Concepts

M. Abdulla

2.3 International NAV Standards For the sake of uniformity of the air NAV, international bodies have formed standards.

www.faa.gov

www.icao.int

www.iata.org

www.fcc.gov

www.itu.int

www.tc.gc.ca

www.arinc.com

Figure-2.8 Logo of national and international bodies

•

International Civil Aviation Organization (ICAO): It is a UN organization that has the following responsibilities: 1) 2) 3) 4)

Develop standards for aviation matters. Recommend specific systems7. Provides international agreements for ATC. Defines country airspace. That is which country has responsibility over the ocean, etc.

•

International Air Transport Association (IATA): Represents the interest of commercial airlines.

•

International Telecommunication Union (ITU): Recommends all allocations of frequencies in the radio spectrum.

•

National Aviation: ICAO, IATA, and ITU work closely with national bodies such as: 1) Canada: ™Transport Canada Civil Aviation (TCCA) ™Industry Canada

7

But not a specific Hardware (HW).

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Chapter 2: Basic Concepts

M. Abdulla

2) United States: ™Federal Aviation Administration (FAA) ™Federal Communication Commission (FCC) ™Aeronautical Radio Inc. (ARINC): Private association for US-airlines; however, since the US dominate the world airline business ARINC standards are used worldwide.

2.4 Airspace Structure For effective and safe ATC, the airspace is organized according to its specific purpose and use. The sky is divided into Controlled Airspace [Classes A, B, C, D, & E] and Uncontrolled Airspace [Class G]. 18.2 km 13.6 km

Class-A

J-Airway

5.5 km Continental Control Area

Class-E

4.4 km

55.5 km

V-Airway

8.0 km

Class-C

0.4 km 0.2 km

1.2 km

9.3 km

Class-B

Non-Tower Airport

Class-D

4.7 km

Transition Area

Class-G

Class-G

0.9 km 0.4 km

Class-G

Figure-2.9 Airspace structure for Canada and the US as of 1991 [K6-3]

•

Some Definitions: 1) 2) 3) 4)

Mean Sea Level (MSL): Represents the Altitude (ALT) above the earth surface w.r.t sea. Above Ground Level (AGL): Represents the ALT above the earth surface w.r.t GND. Flight Level (FL) Statue Mile (sm)

ft MSL > ft AGL FL1 ≡ 100 ft MSL 1 sm = 0.869 nm = 1.609 km •

Class A: Positive Control Area (PCA): 1) 2) 3) 4)

ABOVE all airspaces. From FL180 to FL600. A/C is controlled with Instrument Flight Rules (IFR). Radio communication with ATC before entering this zone is required. 15

(2.6) (2.7) (2.8)

Chapter 2: Basic Concepts •

Class B: Terminal Control Area (TCA): 1) 2) 3) 4) 5) 6) 7) 8)

•

Airspace is similar to class B but for smaller CITIES. Lightweight airplanes cannot fly here (special permission from ATC may be granted). Control tower is equipped with radar. Uppermost circle radius = 5 nm = 9.3 km. Maximum airspeed = 250 kts. A/C must have a 2-way VHF radio and a mode-C transponder. Radio communication with ATC before entering this zone is required.

Class D: Airport Traffic Area (ATA): 1) 2) 3) 4) 5) 6) 7)

•

Airspace in the vicinity of major busy airports in BIG cities. Lightweight airplanes cannot fly here (special permission from ATC may be granted). Uppermost circle radius = 30 nm = 55.5 km. Maximum airspeed = 250 kts. A/C must have a 2-way VHF radio and a mode-C transponder. IFR aircrafts must have VOR equipment. Visual Flight Rules (VFR) corridors are sometimes designated. Radio communication with ATC before entering this zone is required.

Class C: Airport Radar Service Area (ARSA): 1) 2) 3) 4) 5) 6) 7)

•

M. Abdulla

Airspace in the vicinity of very small or DIMINUTIVE airports. Lightweight airplanes may fly here (unless specified otherwise). Control tower may not be equipped with radar. Circle radius = 5 sm = 4.4 nm = 8.0 km. Maximum airspeed = 250 kts. A/C must have a 2-way VHF radio and a mode-C transponder. Radio communication with ATC before entering this zone is required.

Class E: Contains Remaining Controlled Airspaces: 1) This airspace is EVERYWHERE due to its vast volume. 2) Lightweight airplanes may fly here (unless specified otherwise). 3) Airspace categories:

™Continental Control Area: From FL145 to FL180 (Bottom of Class A). ™Transition Area: Transition between Airport and En-route environment. From 700 ft AGL to 1200 ft AGL. ™Non-Tower Airport Area: Communication with ATC is recommended.

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Chapter 2: Basic Concepts •

M. Abdulla

Class G: Completely Uncontrolled Airspace: 1) Low flying GND airspace. 2) Lightweight airplanes may fly here freely. 3) ATC does not have authority for traffic control.

Airspace Communications Separation Class with ATC for Entry Provided

Minimum Qualifications

A

Required

All A/C

Instrument Rating

B

Required

All A/C

Private or Student Certificate dependent on location

C

Required

D

Required

E

Not Required for VFR

G

Not Required

VFR from IFR Runway Operations None for VFR None

Student Certificate Student Certificate Student Certificate Student Certificate

Figure-2.10 Airspace summary [K6-3]

•

Special Use Airspace: 1) 2) 3) 4) 5) 6) 7)

•

Warning Area (W): Area outside territorial limits (e.g. Over international water). Alert Area (A): Area with high volume of aerial activity (e.g. Pilot training). Prohibited Area (P): Flight is prohibited for security reasons (e.g. White House). Restricted Area (R): Flight is restricted for safety reasons (e.g. Area where guns are used). MIL Operations Area (MOA): Separate Civilian (CIV) traffic from MIL training activities. MIL Training Route (MTR): Low amplitude/high speed MIL flight training. Air Defense Identification Zone (ADIZ): Area where identification (ID) is required for national security reasons. If A/C does not respond it may be shot.

Oceanic Control Areas: 1) Airspace over ocean, outside individual countries. 2) Airspace is similar to class A. 3) Traffic control is the responsibilities of adjacent countries identified by ICAO8.

•

Airway: 1) It is a highway in the sky. 2) Directions to fly along this highway are given by signal radiation of VOR or VORTAC GND stations.

8

As an example, the Caribbean area is under US responsibility.

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Chapter 2: Basic Concepts

M. Abdulla

3) Airway width = 10 sm = 16 km. 4) Airway types:

™V-Airway: ¾Synonyms: V or VOR or Victor Airway. ¾Located in class E airspace (till FL180). ¾For short-trip / low ALT flights. ¾Used by IFR and VFR A/C. ™J-Airway: ¾Synonyms: J or Jet or Juliet Airway. ¾Located in class A airspace (From FL180 to FL450). ¾For long-trip / high ALT flights. ¾Used by IFR A/C.

Ground Station

Figure-2.11 V- or J-Airway NAV (i.e. without using waypoints)

2.5 Air Traffic Control System The purpose of ATC is to promote safety and order in the sky. Also, ATC system is similar worldwide due to ICAO standardization. •

ATC achieves its duties by managing and manipulating the following: 1) Systems: ™A/C. ™Airport systems. ™NAV systems. ™Traffic control devices. ™GND equipments. ™Etc. 2) Information: ™Apply rules and procedures. ™Provide weather information. ™Enable communication with aircrafts. ™Etc.

18

Chapter 2: Basic Concepts •

ATC complexity are due to: 1) 2) 3) 4)

•

M. Abdulla

Traffic density Weather conditions Cost considerations Available technology

ATC facilities include: 1) Air Traffic Control Tower Center (ATCTC): Handles traffic around the airport. ™GND Control 2) Terminal Radar Approach Control (TRACON): Handles traffic in the terminal area. ™Departure control ™Approach control 3) Air Route Traffic Control Center (ARTCC): Handles En-route traffic. ™En-route Control 4) Flight Service Station (FSS): ™Flight planning. ™Traffic condition bulletins. ™Weather information. ™Status of Navigational Aid (NAVAID) reports. ™Handling certain non-tower airport traffic. ™Communication with VFR flights. ™Coordination of search operations.

•

MIL ATC: 1) MIL ATC works closely with CIV ATC. 2) MIL ATC facilities include: ™Radar Approach Control Facility (RAPCON): US Air Force. ™Radar Air Traffic Control Center (RATCC): US Navy.

2.5.1 Visual Flight Rule – VFR •

Definition: VFR is based on flying by visually looking out of the cockpit to navigate with reference to GND landmarks and to avoid collisions with other A/Cs.

•

VFR A/C can voluntarily access various ATC services: 1) 2) 3) 4)

Radar traffic information service Radar assistance: Obtain NAV vectors. Terminal radar service: Merging of VFR and IFR traffic. Tower En-route control: Short VFR flights.

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Chapter 2: Basic Concepts

M. Abdulla

•

VFR Flight Plan: In general, filling a flight plan is not required for VFR A/C; however it is a good practice since it could be useful in search and rescue operations in case an accident or a problem occurs. If a flight plan is filled, we do not need to follow it fully, but if we do it would be better. Canadian authorities are more strict than the US and requires that we fill-in a flight plan.

•

VFR Weather Minima:

500 ft ≈ 152 m

Clouds 500 ft ≈ 152 m

1 mile ≈ 1.6 km 500 ft ≈ 152 m

Sea Level Figure-2.12 VFR weather minima for Canada and the US [K3-3]

2.5.2 Instrument Flight Rule – IFR •

Definition: IFR is based on flying using airborne instruments (not by looking out of the cockpit).

•

Characteristics of IFR Flights: 1) Pilot must have certain qualifications. 2) Pilot and A/C equipment are subject to periodic certification checks. 3) A/C must be equipped with: ™Gyroscope ™Navigational equipments ™Radio communication ™Radar transponder ™Etc.

•

ATC control of IFR traffic is based on 2 methods: 1) Procedural Method: ATC uses real-time position information received from the A/C as it flies over predetermined GND reporting points (e.g. VOR stations).

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Chapter 2: Basic Concepts

M. Abdulla

2) Radar Method: ATC uses continuous position information obtained from GND based radars. This method is more precise; therefore, closer A/C separation distances are possible.

small

small

Figure-2.13 Radar method enables small separation distances

•

IFR Traffic Separation: 1) ATC performs traffic separation for IFR A/C only (not VFR). 2) IFR separation is highly dependent on: ™ALT ™A/C speed. ™Airborne NAV equipment used. ™Control method used (Procedural or Radar). ™Etc.

IFR Flight Phases:

p De

ur ar t

t ro on C e

l En-r

Ground Control

oute Cont ro

Terminal Area

Terminal Area

•

Ap

l

c oa pr

h

l t ro n Co

Ground Control Figure-2.14 IFR flight phases [K3-4]

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Chapter 2: Basic Concepts

M. Abdulla

1) Departure: ™Pilot communicates with Clearance Delivery. ™Departure transponder code is assigned. ™Transfer to GND Control for taxi clearance to the active runway. ™Transfer to Tower Control when A/C is ready to takeoff. ™Transfer to Departure Control when A/C is airborne until the end of Terminal Area. 2) En-route: ™Transfer to En-route Control during transition airspace. ™As the flight proceeds the A/C is handed-over from one ARTCC to another. ™Pilots are required to follow their routes & ALT, and report their position. ™Change of route may be requested dues to weather or other circumstances. ™While flying over the ocean, the rules and regulations of ICAO and the country controlling the airspace must be followed9. 3) Arrival and Landing: ™Before arriving to the airport, ARTCC contacts Approach Control.

™Transfer to Approach Control is done in 2 methods: ¾Holding Fix Method: Use when the sky is busy. ¾Radar ID Method: Transfer is done in a predetermined area. ™Transfer to Tower Control when A/C is ready to land using ILS. Also at this stage, VFR A/C which land visually are mixed with IFR airplanes; therefore, first come first serve principle is applied. ™Transfer to GND Control for taxi clearance to the active gate.

Radio Wave

1,000 ft ≈ 305 m

Runway Holding Fix

Outer Middle Marker Marker

Figure-2.15 Holding fix method and ILS for the landing phase [K3-5] 9

As an example, North Atlantic permits only IFR fights.

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Chapter 2: Basic Concepts

M. Abdulla

2.5.3 VFR and IFR •

Flight Planning: A flight plan is prepared filled either in person, by telephone, or by radio with FSS. 1) A/C ID (registration sign). 2) Type of flight plan (VFR or IFR). 3) A/C NAV equipments. 4) Route of flight (V or J-Airway). 5) Departure point. 6) Destination point. 7) Departure time (in GMT). 8) En-route estimated time. 9) Fuel onboard (in terms of endurance time). 10) Cruising ALT (for IFR you request the ALT). 11) True airspeed (kts). 12) Number onboard (crew + passengers). 13) Color of A/C. 14) Alternate airport (mandatory for IFR). 15) Remarks as necessary. 16) Pilot’s Info: Name / License # / Address / Telephone #

•

Cruising ALT: Specific cruising ALT must be respected depending on the A/C HDG. IFR

VFR

0000 Æ 1790

1800 Æ 3590

0000 Æ 1790

1800 Æ 3590

FL30 § 0.914 km FL50 § 1.52 km FL70 § 2.13 km FL90 § 2.74 km FL110 § 3.35 km FL130 § 3.96 km FL150 § 4.57 km FL170 § 5.18 km FL190 § 5.79 km FL210 § 6.40 km FL230 § 7.01 km FL250 § 7.62 km FL270 § 8.23 km FL290 § 8.84 km FL330 § 10.06 km FL370 § 11.28 km FL410 § 12.50 km Etc

FL20 § 0.610 km FL40 § 1.22 km FL60 § 1.83 km FL80 § 2.44 km FL100 § 3.05 km FL120 § 3.66 km FL140 § 4.27 km FL160 § 4.88 km FL180 § 5.49 km FL200 § 6.10 km FL220 § 6.71 km FL240 § 7.32 km FL260 § 7.93 km FL280 § 8.53 km FL310 § 9.45 km FL350 § 10.67 km FL390 § 11.89 km Etc

FL35 § 1.07 km FL55 § 1.68 km FL75 § 2.29 km FL95 § 2.90 km FL115 § 3.51 km FL135 § 4.12 km FL155 § 4.72 km FL175 § 5.33 km FL195 § 5.94 km FL215 § 6.55 km FL235 § 7.16 km Etc

FL25 § 0.762 km FL45 § 1.37 km FL65 § 1.98 km FL85 § 2.59 km FL105 § 3.20 km FL125 § 3.81 km FL145 § 4.42 km FL165 § 5.03 km FL185 § 5.64 km FL205 § 6.25 km FL225 § 6.86 km Etc N

D 360D 000

270D

W

E

S

180D

Figure-2.16 VFR and IFR cruising ALTs [K6-4]

23

090D

Chapter 3 Early NAV

No human investigation can claim to be scientific if it doesn’t pass the test of mathematical proof. — Leonardo Da Vinci

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Chapter 3: Early NAV

M. Abdulla

3.1 Flight Controls Spoiler Vertical Trim Rudder Ruder Trim Tab

Aileron Aileron Trim Tab

Center of Gravity Slat Roll X-longitudinal Pitch

Elevator Trim Tab Elevator

Flap

Horizontal Stabilizer

Wing

Y-lateral

Yaw Z-vertical Figure-3.1 A/C control surfaces [K1-1]

Pitch (Elevator)

Yaw (Rudder)

Figure-3.2 A/C 6-degrees of freedom [K2-1]

25

Roll (Aileron)

Chapter 3: Early NAV •

M. Abdulla

Movement Control: 6 degrees of freedom. 1) Roll: Rotation movement of an A/C about a longitudinal axis (X). ™Hardware: Aileron. ™Control: Lateral motion of the stick. 2) Pitch: Rotation movement of an A/C about a lateral axis (Y). ™Hardware: Elevator. ™Control: Longitudinal motion of the stick. 3) Yaw: Rotation movement of an A/C about a vertical axis (Z). ™Hardware: Rudder. ™Control: Rudder pedals.

•

Lift and Drag: Affects the A/C movement in the X and Z axes. ™Hardware: ¾Flaps ¾Slats ¾Spoilers

•

Thrust: That is the driving force of the A/C is accomplished by the power-plant control.

Rool to the Left

Rool to the Right

Left

Right

Pitch Up

Pitch Down

Push Pull

Yaw to the Left

Yaw to the Right

Right Pedal

Left Pedal

Figure-3.3 Controlling A/C 6-degrees of freedom

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Chapter 3: Early NAV

M. Abdulla

3.2 Basics of Flight Instruments The purpose of A/C instruments are to provide the pilot with critical information for safe and effective operation of the vehicle. •

Basic-Six or Basic-T: 1) Pitot Static Instruments: 1, 2, 3 2) Attitude Instruments: 4, 5 3) HDG Instruments: 6, 7

Airspeed Indicator

Artificial Horizon

Altimeter

1

4

2

Turn & Bank Indicator

Directional Gyroscope

Vertical Speed indicator

5

6

3

+

Magnetic Compass 7

Figure-3.4 Basic flight instruments [K6-5]

3.2.1 Pitot Static Instruments •

Preliminary Concept: 1) Pitot Static Instrument System: Device driven by static pressure and pitot pressure obtained from the pitot static tube. 2) Pitot Static Tube: It is an open-ended tube where moving fluid flows in order to measure the stagnation pressure. Pitot static tube is mounted under the wing. 3) Bernoulli Equation at Constant Elevation: Assuming ideal uncompressible fluid.

Pd =

ρV

2

2 Pt = Ps + Pd 27

(3.1) (3.2)

Chapter 3: Early NAV

V :

Speed.

ρ:

Air density.

M. Abdulla

Ps : Static pressure. Pd : Dynamic pressure. Pt :

Pitot or total or stagnation pressure. Airspeed Indicator

Altimeter

15 10

45 20 40

35 30 25 5

Vertical speed Indicator

0 1 8 7

1

2

9

3 6

12 3

5

2

3 4 4

0

4 1

2

3

Drain Static Pressure Line Electrical Contacts for Heater

Pitot Pressure Line

Pitot-Static Tube Ps = Static Pressure

Pt = Pitot Pressure

Heater Drain

Figure-3.5 Pitot static instrument system [K3-6]

•

Useful Equations: 1) Equation of state for perfect gases:

P : Pressure [ Pa ] .

P = ρ RT

(3.3)

K D = 273.16 + D C

(3.4)

T : Temperature ª¬ K D º¼ . 2 R : 287.05 ª« m 2 D º» . ¬ sK ¼

ρ : Atmospheric Air density ª kg ¬«

º. m3 ¼»

28

Chapter 3: Early NAV

M. Abdulla

2) Sea Level Values: Measured on a standard day in Mediterranean referred to as Standard ICAO.

Temperature:

T 0 = 15 D C = 59 D F = 288.16 K D

Speed of Sound:

a0 = 340.0 ª m º = 1116.2 ªft º ¬ s¼ ¬ s¼ ρ 0 = 1.225 ª kg 3 º = 0.002377 ªslug 3 º «¬ m »¼ «¬ ft »¼ P0 = 1 [ atm ] = 101,325 [ Pa ] = 1013.25 [ mbar ] = 29.92 [ in Hg ]

Density: Pressure:

(3.5)

3) Equations: Takeoff and landing are extremely related to pressure. As a result, flights are mostly in early morning or at night since temperature is low at that time. ↓ Temperature ∴ ↑ Pressure ∴ ↑ Speed ∴ ↓ ALT

Speed of Sound:

§ a · § T st · ¨ ¸=¨ ¸ © a0 ¹ © T 0 ¹

Density:

§ ρ · § T st · ¨ ¸=¨ ¸ © ρ0 ¹ © T 0 ¹

Viscosity:

4.25

§ P · § T st · ¨ ¸=¨ ¸ © P0 ¹ © T 0 ¹ § µ · T st1.5 (T 0 + 120 ) ¨ ¸= © µ0 ¹ T 0 (T st + 120 )

← Temperature ª¬ K D º¼

­ ½ ° Altitude [ m ] ° ° ° D ®Temperature ª¬ K º¼ ¾ ° ° o ° ∆ = ∆ kelvin = −0.0065 ª K º ° «¬ m ¼» ¿ /¯ T st −T 0 ) ( OR H = ∆ 2­ ½ °Altitude [ ft ] ° ° ° D ®Temperature ª¬ C º¼ ¾ ° ° D °∆ = ∆celsius = −0.00198 ª C º ° ¬« ft ¼» ¿ ¯ 10

(3.6)

0.5

5.25

Pressure:

10

(3.7)

(3.8)

The relation between ALT and temperature is not at all times linear and proportional, and the best proof for that are the two layers of atmosphere known as the troposphere and the mesosphere. For more on ALT, temperature, pressure w.r.t. the atmosphere refer to Appendix C.

29

Chapter 3: Early NAV

M. Abdulla

4) Several Definitions of ALT:

™Ha = Absolute ALT: Height above earth surface. ™Ht = True ALT: Height above sea level but with Standard ICAO values. ™Hd = Density ALT: Height above sea level with ambient density.

H d = Height Above Sea Level ρ = actual ambient density (i.e. now)

(3.9)

™Hp = Pressure ALT: Height above sea level with ambient pressure.

H p = Height Above Sea Level

P = actual ambient pressure (i.e. now)

(3.10)

™Standard ICAO: The ambient pressure and density are always less than the Standard ICAO ones.

H = Altitude

­ρ ½ ® < 1¾ → { ρ < ρ 0 } ¯ ρ0 ¿ ­P ½ ® < 1¾ → {P < P0 } ¯ P0 ¿

Ht → 0.2

0.4

0.6

0.8

1.0

§ ρ · §P · ¨ ¸ or ¨ ¸ © P0 ¹ © ρ0 ¹

Figure-3.6 Height versus pressure or density

­H d ° ® °¯ H p

­H d ° ® °H p ¯

ρ = ρ0 P = P0

= Ht ½ ° ¾ →∴ @ Standard ICAO: {H t = H d = H P } = Ht ° ¿

ρ ≠ ρ0 P ≠ P0

> Ht ½ ° ¾ > Ht ° ¿

30

(3.11)

(3.12)

Chapter 3: Early NAV •

M. Abdulla

Airspeed Indicator (AI): To obtain the speed we measure the difference between the pitot and the static pressure, i.e. we obtain the dynamic pressure.

­° ­ ρV 2 ½ ® Pd = Pt − Ps = ¾ → ®V = 2 ¿ °¯ ¯

2Pd °½ ¾ ρ ¿°

(3.13)

1) Indicated Airspeed (IAS): Uncorrected speed. 2) Calibrated Airspeed (CAS): Airspeed corrected for instrument error and pitot static system error. 3) Equivalent Airspeed (EAS): Airspeed corrected for compressibility error. This error is negligible up to 250 kts and 10,000 ft § 3.05 km. 4) True Airspeed (TAS): Airspeed corrected for air density error.

TAS = CAS

•

ρ0 ρ

Altimeter: It is a barometer that measures the change in pressure ALT, and outputs the elevation height. Altimeter11 could be set to different pressure modes for a specific ALT reading: 1) Pressure at Nautical Height (QNH): ™Pressure Type: Sea level pressure. ™Used for: ¾Takeoff ¾Landing ¾VFR Flying 2) Pressure at Standard Sea Level (QNE): ™Pressure Type: Standard sea level pressure (i.e. 1 atm). ™Used for: ¾High ALT flying. ¾Unpopulated area flying. 3) Pressure at Field Elevation (QFE): ™Pressure Type: Airfield pressure. ™Used for: ¾Aerobatic flying.

11

(3.14)

To avoid traffic conflict and to ensure security in the sky, the same altimeter setting should be used for a given region.

31

Chapter 3: Early NAV •

M. Abdulla

Vertical Speed Indicator (VSI): It measures the change in pressure ALT and outputs the vertical speed. If the A/C flies straight, the pressure is constant and hence, VSI is set to zero.

Increase Static Pressure:

Decrease Static Pressure:

↓ H ∴ ↑ Ps

↑ H ∴ ↓ Ps

Figure-3.7 Static pressure variation with vertical motion

3.2.2 Attitude Instruments These instruments are based on using a gyroscope12 to indicate the roll and pitch of an A/C. •

Artificial Horizon: A gyro operated instrument that shows the roll X-axis and pitch Y-axis attitudes of an A/C w.r.t. an artificial reference line horizon of earth. The gyro spins on the yaw Z-axis. Also, the gyro can be driven either by vacuum air turbine or electric motor.

•

Turn and Bank Indicator: A gyro-operated instrument that is driven either by vacuum air turbine or electric motor. This was the first gyro that made blind flying possible. This instrument contains 2 independent mechanisms:

1) Gyro driven pointer: This pointer indicates the rate of turn of the A/C.

Left

Right

Figure-3.8 Rate of turn of the A/C

12

Gyroscope or Gyro is a rotating device that will maintain its original plane of rotation no matter which direction the A/C is turned.

32

Chapter 3: Early NAV

M. Abdulla

2) Detect slip and skid in the turn: There is a ball placed in a fluid filled curve-tube in the turn and bank indicator. If we travel straight the ball stays in the middle. To make a turn in a stable way, we must turn while making sure that the ball remains in the middle. This means that g and centrifugal acceleration are perpendicular.

R

L

SLIP

Figure-3.9 Turn and bank indicator [K6-6]

3.2.3 HDG Instruments These instruments are used to indicate the A/C HDG.

Directional Gyroscope (DG): This instrument displays the A/C yaw angle. The gyro rotates about the pitch Y-axis and it is suspended in 2D Y-Z-axis. The gyro can be driven either by vacuum air turbine or electric motor.

E

S

N

W

•

Setting Knob Figure-3.10 Directional gyroscope indicator [K6-7]

1) The HDG can be set by the setting knob. 2) DG should be reset every 10 to 15 minutes (modern DGs reset automatically).

33

Chapter 3: Early NAV

M. Abdulla

3) DG error are caused by: ™Earth rotation (150 / hr). ™Turn, Bank, and Pitch. ™Gyro bearing friction. •

Magnetic Compass: This instrument displays the A/C horizontal direction or HDG w.r.t. earth magnetic meridian. Today, the compass principle is applied in modern navigational displays as: Radio Magnetic Indicator (RMI) and Horizontal Situation Indicator (HSI)13. Magnetic Compass errors are: 1) Static Error: Magnetic pole and the true geographical pole are not at the same location. A compass always points to the magnetic north pole, hence a static error.

™Magnetic pole rotates slowly around the true pole (1 rev. / 1000 years). ™Magnetic variation: Difference between the true and magnetic HDG. ™In Montréal: ¾Magnetic variation = 150 W. ¾This means that the magnetic North is 150 to the West of the true North. ¾True HDG of magnetic north = 360 – 15 = 3450. 2) Dynamic Error: Magnetic meridian has important dips in high LAT because after all earth is not spherical; therefore, the compass card deviates from its horizontal position; hence, the Center of Gravity (CG) changes, resulting in dynamic error. If an A/C is traveling say to the East; when the plane:

™Accelerate: the compass display the HDG but more tilted to the North. ™Decelerate: the compass display the HDG but more tilted to the South. Magnetic North Pole

True North Pole

15D

Meri

dian

DIP Angle

n Mag

etic

DIP Angle = 0

Not a perfect Parallel Figure-3.11 Earth Magnetic field [K6-8]

13

RMI and HSI will be discussed further in Chapter 5.

34

Chapter 3: Early NAV

M. Abdulla

3) Deviation Error: Airplanes are constructed in general from metals14 (i.e. aluminum alloy) which could potentially be affected by the earth magnetic field and/or airborne avionics; therefore, an electromagnetic (EM) field will be generated, hence deviation error.

™Adjustable magnets: are used to compensate the deviation error. ™Compass swinging: should be performed annually to the compass to correct the deviation error.

N 0

E 0

0

0

S 0

0

0

W 0

0

0

True HDG 000 / 360 030 060 090 120 150 180 210 240 2700 3000 3300 Displayed HDG 0030 0310 0610 0900 1220 1470 1790 2090 2410 2700 2980 3340 Deviation Error - 30 - 10 - 10 00 - 2 0 + 3 0 + 1 0 + 10 - 1 0 00 + 20 - 40 Figure-3.12 Compass deviation error [K3-7]

3.3 Pilotage and Dead Reckoning •

Preliminary Concept: 1) True Airspeed (TAS): Airspeed w.r.t. air. 2) HDG: Angle between A/C longitudinal axis and the meridian axis, measured clockwise from the meridian (i.e. from North). HDG is used in correspondence with TAS. 3) Ground Speed (GS): Airspeed w.r.t. GND. 4) TK: Angle between GS vector and the meridian axis, measured clockwise from the meridian (i.e. from North). TK is used in correspondence with GS. 5) Wind: It is determined by its speed or Wind Speed (WS) and direction or Wind Angle (WA). Top View N W

E

Win d

Meridian Axis

S

TAS HDG GS

TK WA WS

Figure-3.13 Definition of speed vectors 14

Recently a lot of Research and Development (R&D) efforts are underway to adapt the use of composite materials instead of the traditional aluminum alloy core. The major disadvantage of this transformation is the high cost of composite materials.

35

Chapter 3: Early NAV

M. Abdulla

6) Drift Angle (į): Angle measured by going from the HDG to the TK. 7) Bearing: Angle of an object seen from the A/C measured clockwise from the meridian (i.e. from North). •

Going from A to B:

TK Made Good α

γ

β

A

B

Required TK Figure-3.14 Distinction between Required TK and TK Made Good [K3-8]

1) 2) 3) 4) 5)

•

Required TK: Angle representing the proposed A/C path over GND. TK Made Good: Angle representing the actual A/C path over GND. Opening Angle (Į): Angle representing the departure TK Error. Closing Angle (ȕ): Angle representing the destination TK Error. TK Error (Ȗ): Angle representing the difference between the Required TK and TK Made Good.

100 Drift Lines:

Required TK

A

10D 10D

20 nm

10 nm

10D 10D

B

Figure-3.15 100 Drift Lines [K3-9]

1) 100 Drift Lines are drawn around the Required TK to help: ™NAV ™Estimate wind drift 2) 100 nm marks are identified along the Required TK to help the estimate of GS. 3) It is recommended to perform a GS check every 10 nm.

36

Chapter 3: Early NAV •

M. Abdulla

Double TK Error Method: 10 d

ne rift li 150D − 6D = 144D

B A

6

2 × 6 D = 12 D

Required TK

D

C K eep Tra this d veling in irecti on 10 d rift li n

Wind

150D

156D

e

Figure-3.16 Double TK Error Method [K3-10]

1) Method is used to regain Required TK. 2) Due to crosswinds we deviate from the Required TK by say 60. 3) To regain the Required TK we travel in the opposite direction by 2 x 60. The first 60 is to get back to the Required TK, and the next 60 is to compensate for future crosswinds. 4) The time it takes to fly from A to B to C is approximately the same time it takes to fly from A to C. •

Visual TK Alteration Method: 10 d

ne rift li 150D − 6D = 144D

B

Required TK

6D

A

Landmark

C

10 d

Wind

6D Keep T ra this d veling in irecti on

rift li ne

150D

156D

Figure-3.17 Visual TK Alteration Method [K3-10]

1) 2) 3) 4)

Method is used to regain Required TK based on finding a landmark. Due to crosswinds we deviate from the Required TK by say 60. We locate a landmark on the Required TK (C) and fly toward it. At the Required TK, we go south by 60 to overcome future crosswinds.

37

Chapter 3: Early NAV •

M. Abdulla

Two Point Visual Range Method: TV Tower

A

Light House

Radio Tower

Required TK

B

Figure-3.18 Two Point Visual Range Method

1) Method is used to fly on the Required TK through visual reference to landmarks. 2) Locate a landmark on the Required TK and fly toward it. 3) Repeat this procedure until destination is reached. •

Opening/Closing Angles Method: Wind

rift lin 10 d

10 d rift li n

e

A

4 10 d rift li

D

e

Required TK

ne

150D

B n rift li 10 d

ling in Trave Keep irection this d C

D

8

e

150D − ( 4D + 8D ) = 138D

Figure-3.19 Opening/Closing Angles Method [K3-11]

1) 2) 3) 4) •

Method is used if we determine late in the travel that we are off the Required TK. Due to crosswinds we deviate from the Required TK by say 40. Late in the travel at point B we estimate the Opening Angle (40) and the Closing Angle (80). To reach C we travel in the opposite direction by 40 + 80.

Return to Point of Departure Method: 1) Method is used if we suddenly detect a problem during NAV and want to turn back. 2) Main reasons to use this method are: ™Weather conditions ™Mechanical problems ™Etc. 3) Estimate GS, determine the TK angle, and calculate į. 4) Calculate the Reciprocal TK. Reciprocal TK = TK ± 1800

38

(3.15)

Chapter 3: Early NAV

M. Abdulla

5) Finally obtain the Reciprocal HDG Reciprocal HDG = Reciprocal TK + δ

(3.16)

N Fly at this Direction

TAS

Re

cip r

Wind

DG lH ca ro cip Re

GS

δ

oc al

TK

W

E

HD G

δ

TAS

TK

GS

S

Figure-3.20 Return to Point of Departure Method

•

Triangulation Method: TV Tower N Light House

Light House Bearing

TV Tower Bearing

Figure-3.21 Triangulation Method [K1-2]

39

Chapter 3: Early NAV 1) 2) 3) 4)

M. Abdulla

Method is used to determine the A/C position. We identify 2 or more landmarks and determine their bearings. We then extend their lines. The point where the lines intersect is where the aircraft is located.

40

Chapter 4 Air Communication

The man who does things makes many mistakes, but he never makes the biggest mistake of all — doing nothing. — Benjamin Franklin

41

Chapter 4: Air Communication

M. Abdulla

4.1 Radio Wave Propagation •

Definition: 1) On Earth: There exist 2 method of propagation: GND Wave and Sky Wave. 2) In Free-Space: Propagation occurs in straight line or Line Of Sight (LOS) Wave. 3) Ionosphere Layer15: A region of the earth atmosphere containing gas molecules that absorbs incoming solar radiation of X-ray16 frequencies and above to reach earth. Ionosphere Layer

Sky Wave Ground Wave

Tx Station

Earth Figure-4.1 GND and sky wave propagation [K6-9]

4.1.1 GND Wave •

Frequency: 0 to 3 MHz (Covers the following bands: ELF, SLF, ULF, VLF, LF, and MF)

•

Wave Characteristics: 1) Wave Location: The signal is in proximity to the earth surface. 2) At Lower Frequencies (ELF, SLF, ULF, VLF, and LF): ™Propagation velocity  constant ™Interference may occur due to atmospheric noise ™Provided sufficient Tx power is available: Max Range § 5,000 miles § 8,000 km ™Optimum antenna size: height § half wavelength = Ȝ / 2 = velocity / (2 × frequency) 3) At Higher Frequencies (MF): ™The power received is smaller than the power transmitted; therefore we obtain a larger attenuation factor.

15 16

For more on the atmosphere layers refer to Apendix C. X-ray bandwidth varies from: 3x107 to 3x109 GHz.

42

Chapter 4: Air Communication

M. Abdulla

Sky Wave

LOS Wave

N/A

GND Wave

BAND MEANING FREQUENCY WAVE ELF Extremely Low Frequency 3 --- 30 Hz SLF Super Low Frequency 30 --- 300 Hz ULF Ultra Low Frequency 300 --- 3000 Hz VLF Very Low Frequency 3 --- 30 kHz LF Low Frequency 30 --- 300 kHz MF Medium Frequency 300 --- 3000 kHz HF High Frequency 3 --- 30 MHz VHF Very High Frequency 30 --- 300 MHz UHF Ultra High Frequency 300 --- 3000 MHz Super High Frequency SHF 3 --- 30 GHz EHF Extremely High Frequency 30 --- 300 GHz Figure-4.2 Frequency band classification [K6-10]

1 L4

(4.1)

§W R · ¸ ©W T ¹

(4.2)

[W R ]Ground wave ∝ α = 10 log10 ¨ Signal attenuation [ dB]. W R : Power received [ Watts ] . W T : Power transmitted [ Watts ] .

α:

L:

Distance between Tx and Rx.

Frequency Over Sea-Water kHz 150 300 500 1,000 2,000 5,000

100 miles 1,000 miles dB dB - 40 - 88 - 40 - 99 - 40 - 108 - 42 - 125 - 44 ......... - 47 .........

Over Earth 100 miles 1,000 miles dB dB - 45 - 105 - 51 ......... - 65 ......... - 82 ......... - 99 ......... - 117 .........

Figure-4.3 GND wave signal attenuation [K3-12]

43

100 miles ≈ 161 km 1, 000 miles ≈ 1, 610 km

M. Abdulla

Received Signal Strength

Chapter 4: Air Communication

Sky Wave

Ground Wave

L

Figure-4.4 Received signal power versus “L” [K1-3]

4.1.2 Sky Wave •

Frequency: 0 to 30 MHz (Covers the following bands: ELF, SLF, ULF, VLF, LF, MF, and HF)

•

Wave Characteristics: 1) Wave Location: The signal is in the sky based on the reflective property of the ionosphere layer. 2) During Nighttime: ™Ionosphere layer is closer to the earth surface. ™Sky wave travel at a flatter angle. ™Advantage: Larger signal distances. ™Disadvantage: More skip zones with no reception will exist. 3) During Daytime: ™Ionosphere layer is farther away from the earth surface. ™Sky wave travel with an angle. ™Disadvantage: Smaller signal distances. ™Advantage: Less skip zones with no reception will exist.

[W R ]Sky wave ∝ L

44

(4.3)

Chapter 4: Air Communication

M. Abdulla

4.1.3 LOS Wave •

Frequency: 30 to 300,000 MHz (Covers the following bands: VHF, UHF, SHF, and EHF)

Ground Wave

Sky Wave

LOS Wave

f 0

3 MHz

30 MHz

300 GHz

Figure-4.5 Frequency bandwidth for GND, sky, and LOS waves

•

Wave Characteristics: 1) 2) 3) 4)

LOS wave travels in a straight line. Propagation follows the laws of free-space. Propagation velocity = constant = speed of light = c = 3 × 108 [m/s] In the VHF band the LOS signal may be affected by the reflection of various objects on earth.

Tx

L

Tx

Rx

Area of Antenna = A

Rx H L=2H

Figure-4.6 Graphical definition of “L”

ªW R º Area of Antenna A = = « » Sphere Area 4π L 2 ¬W T ¼ LOS wave

45

(4.4)

Chapter 4: Air Communication

M. Abdulla

Tx

Rx

T

h

hR

R = Maximum Range

Figure-4.7 Maximum LOS range due to earth curvature [K6-11]

R = 1.2

Maximum LOS Range [ nm ].

R:

(

hT + hR

)

(4.5)

hR : Height of Rx [ ft ]. hT : Height of Tx [ ft ].

Frequency Over Sea-Water All Frequencies

100 miles 1,000 miles dB dB - 40 - 60

Over Earth 100 miles ≈ 161 km 100 miles 1,000 miles dB dB 1, 000 miles ≈ 1, 610 km - 40 - 60

Figure-4.8 LOS wave signal attenuation [K3-12]

Atmospheric Conditions: Signal attenuation becomes more important at the SHF and the EHF band due to the effect of rain and fog.

Loss Heavy Rain Moderate Rain Light Rain Drizzle dB/m 10-3 10-4 10-5 10-6 10-7

(16 mm/hr)

(4 mm/hr)

(1 mm/hr)

(0.25 mm/hr)

GHz 15 7 3 ......... .........

GHz 37 12 6 3 .........

GHz 100 20 9 4 .........

GHz ......... 43 20 8 4

Loss

FOG

RAIN

•

dB/m 10-3 10-4 10-5 10-6

Visible Distance 100 ft GHz 20 7 ...... ......

200 ft GHz ...... 12 4 ......

500 ft 1,000 ft GHz GHz ...... ...... 20 ...... 7 12 ...... 3

100 ft ≈ 30.5 m 200 f ≈ 61 m 500 ft ≈ 152 m 1, 000 ft ≈ 305 m

Figure-4.9 LOS wave signal attenuation due to atmospheric conditions [K1-4]

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Chapter 4: Air Communication

M. Abdulla

4.2 Communications Speech Signal: There are 2 ways to send a speech waveform: 1) Amplitude Modulation (AM): Amplitude of the carrier signal varies

™Frequency band: MF § 540 – 1800 kHz ™Aviation radio technology is based on AM. 2) Frequency Modulation (FM): Frequency of the carrier signal varies.

AM

Amplitude

Amplitude

™Frequency band: VHF § 88 – 108 MHz

Speech Waveform

FM Speech Waveform

t

Amplitude

t

Amplitude

•

Carrier

Carrier

t

f C → Constant Amplitude → Modulated

f C → Modulated Amplitude → Constant

Figure-4.10 AM and FM modulation techniques [K6-12]

47

Chapter 4: Air Communication

•

M. Abdulla

Headset: Used for radio communications. 1) Interface: Transponder 2) Microphones: Noise canceling 3) Headphones: Use a noise sensor or a phase reversing circuitry to attenuate noise. 4) Activation: Press on the push-to-talk button to start transmission.

Figure-4.11 Noise canceling headset17 [K4-2]

17

The price of this headset is roughly $600 US.

48

Part II Avionics

49

Chapter 5 Short-Range NAVAIDS

Anyone who stops learning is old, whether at twenty or eighty. Anyone who keeps learning stays young. — Henry Ford

50

Chapter 5: Short-Range NAVAIDS

M. Abdulla

5.1 Automatic Direction Finder – ADF •

Principle: Provides A/C bearing w.r.t. a GND station known as Non Directional Beacon (NDB). The bearing is measured clockwise starting from the A/C longitudinal axis and stopping at the segment of the A/C – NDB. Note that the reading obtained in the Flight Compartment (F/C) indicator is a relative18 bearing known as the ADF bearing. To obtain the NDB magnetic bearing we need to perform the following:

{NDB Magnetic Bearing w.r.t. A/C} = {A/C Magnetic HDG} + {ADF Relative Bearing}

(5.1)

N

NDB W

E

HDG : 55D S

ADF : 330D

ADF : 40D

HDG : 85D NDB NDB Bearing = 85° + 330° = 415° = 55°

NDB Bearing = 55° + 40° = 95°

Figure-5.1 Examples illustrating the ADF principle [K6-13]

•

Applications: 1) TK Intercept: To be able to get back to the TK due to crosswind. 2) Station Homing: Travel toward or away from an NDB.

™Wrong Station Homing: ¾ADF bearing is aligned to the A/C longitudinal axis; therefore a dramatic curve will occur due to crosswind.

HDG: 090D ADF: 000D

HDG: 095D ADF: 000D

HDG: 110D ADF: 000D

NDB

Figure-5.2 Wrong station homing [K6-13]

18

Wind

If we are using a fix compass card, then the ADF needle will indicate a relative bearing w.r.t. the A/C nose HDG. However, if a rotating compass card is used, then correction can be made so that the ADF needle will point to the NDB magnetic bearing. Hereinafter we will assume that we are using a fix compass card.

51

Chapter 5: Short-Range NAVAIDS

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™Correct Station Homing: ¾Approximate wind Drift Angle (DA) to get back to TK: į § 5° ¾Approximate an extra angle to overcome future cross-wind once TK is regained: Extra § 3° ¾A/C HDG is corrected to fly at: 90° + 5° + 3° = 98° ¾Notice that the ADF bearing and the A/C longitudinal differ by the Extra angle assigned to counter future wind. ¾Correction is achieved when both the ADF and the HDG needles are constant. HDG: 098D ADF: 357

HDG: 098D ADF: 357D

D

HDG: 090D ADF: 000D NDB

δ ≈ 5D

Wind Figure-5.3 Correct station homing [K6-13]

3) Triangulation Position Fix: To know where the A/C is located.

™Tune ADF-Rx to an NDB ™Obtain the ADF bearing. ™Calculate the NDB magnetic bearing19 ™Calculate the NDB true bearing20 ™Place a corresponding line on the map ™Do the same by tuning to another NDB station ™Extend the lines on the map ™The intersection of the lines provides the 2D position fix21 of the A/C. •

On the GND: 1) Tx: NDB or NDB-DME systems. 2) Frequency: MF § 220 – 550 kHz 3) The NDB sends a Morse ID code to the A/C ADF-Rx.

19

Using equation 5.1. That is, subtract 150 as explained in Figure-3.11. 21 2D position fix means to obtain the LAT and LON of the A/C at that time. 20

52

Chapter 5: Short-Range NAVAIDS

M. Abdulla

Figure-5.4 NDB GND station [K4-3]

•

In the A/C: 1) 2) 3) 4) 5)

Rx: ADF-Rx system. Frequency: MF § 550 – 1750 kHz (commercial AM band) ADF bearing needle points only to the tuned NDB. When A/C flies toward an NDB the ADF bearing pointer indicates 000°. When A/C flies above an NDB the ADF bearing pointer indicates 180°.

Sense Antenna: To detect the signal transmitted by the NDB.

ADF-Rx

Fixed Loops: Based on goniometer which measures angular direction of incoming radio waves.

Figure-5.5 ADF–Rx system [K3-13]

53

Chapter 5: Short-Range NAVAIDS

M. Abdulla

•

Advantage: ADF does not suffer from LOS22 since it operates at the MF band.

•

Disadvantages: 1) Errors: ™GND Wave: error § ± 5° ™Sky Wave23: error § ± 30° 2) Quadrantal Error: ™Based on the bending of radio waves due to the A/C metal structure. ™Swinging is required24. ™Max error § ± 10° 3) Night Effect: ™At night ionosphere layer is low; therefore, strong sky waves, hence large error. ™To minimize errors, at night, it is recommended to limit the use of GND stations. 4) Terrain Effect: ™Based on the reflection or bending of GND waves. ™Mountain Effect: The radio wave signal is reflected from the side of mountains. ™Coastal Effect: As the radio wave goes from land to water, the direction of the signal is changed. 5) Precipitation Static: ™Based on static formed when rain or snow or thunderstorm are in contact with antennas. 6) Icing Effect: ™Based on the accumulation of ice on antennas.

•

Future: GPS should make ADF technology retire.

5.2 VHF Omni-directional Range – VOR •

Principle: Provides A/C radial w.r.t. a GND station. In other words, the VOR system only informs us of the A/C location as an entity seen by a GND VOR-Tx; however, we have no knowledge whatsoever on the HDG of the A/C. The radial of the A/C is obtained by taking the phase difference of 2 signals R & V transmitted by the GND station.

R : Reference Phase Signal

FROM : From the GND VOR-Tx

V : Variable Phase Signal

TO :

P : Phase Difference Between R & V 22

Toward the GND VOR-Tx

The higher the frequency of operation the more the technology will be limited by LOS. It is recommended to not operate ADF system near an NDB to make sure that sky waves will not be involved. 24 Similar to a magnetic compass as described on Page-35. 23

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N

W

M. Abdulla

ξ FROM = {A/C Magnetic Radial w.r.t. VOR-Tx} = P

(5.2)

ξTO = {VOR-Tx Magnetic Radial w.r.t. A/C} = P ± 180°

(5.3)

"TO" coordiante system E

Magnetic North R=V

"FROM" coordiante system

S

V R

R V

R

ξ FROM = P = 270°

V

ξTO = P − 180° = 90°

V R

3600

900

2700

R

VOR-Tx

P R

V

R

0000 / 3600

2700

900

V

R

ξ FROM = P = 120°

12 0 0

1800

1800

R

P

R

ξTO = P + 180° = 300° 3600

R V

V

30

00

900

2700

V

V

1800

V Figure-5.6 Examples illustrating the VOR principle [K6-14]

VOR-Tx No matter A/C HDG, the same VOR data is displayed

ξ FROM = P = 120° ξTO = P + 180° = 300°

Figure-5.7 VOR does not provide A/C HDG; it only gives the radial occupied by the A/C

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Applications: 1) V-Airway: Used to assign highways in the sky. 2) TK Intercept: To be able to get back to the TK due to crosswind. Simply fly toward the needle of the VOR display known as the Course Deviation Indicator (CDI) to ensure that the A/C is going in the direction of the VOR GND station. 3) Triangulation Position Fix: To know where the A/C is located, tune VOR-Rx to at least 2 VOR GND stations and obtain the 2D position fix.

•

On the GND: 1) Tx: VOR-Tx or VOR-DME or VORTAC systems. 2) Frequency: VHF § 108 – 118 MHz ™For Approach NAV: 108 – 112 MHz ™For Short-Range NAV: 112 – 118 MHz ™Number of Channels: 100 3) 2 signals are emitted at the same time: ™Reference Phase Signal: ¾Symbol: R ¾Modulation: FM ¾Rate: 30 Hz ¾Type: Non-directional

™Variable Phase Signal: ¾Symbol: V ¾Modulation: AM ¾Rate: 30 revolutions per second (rps) Ł 30 Hz ¾Type: Rotational 4) The VOR-Tx sends a Morse ID code to the A/C VOR-Rx. 5) VOR-Tx is also used for 2-way voice communication.

Figure-5.8 VOR GND station [K4-4]

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30 rps Has 332 teeth that are not fairly distributed 332 (teeths) x 30 (rps) = 9,960 Hz

Tone Wheel

9,960 ± 480 Hz

Signal

Morse Indent.

R

75% of signal radiation

V

25% of signal radiation

VHF Carrier 108 → 118 MHz

Modulation Eliminator

Voice

Figure-5.9 VOR–Tx system [K3-14]

•

In the A/C: 1) 2) 3) 4)

Rx: VOR-Rx system. Frequency: VHF The phase difference P between R & V is calculated. A/C CDI shows the VOR radial reading. If CDI becomes defective a red flag will appear.

VOR Signal from Tx

Audio Output

CDI P

Detects the Amplitude

Filter 30 Hz

V

Filter 9,960 Hz

R

Phase Comparator

Filter 30 Hz

Limitter

Frequency Discriminator

Eliminate Noise

Frequency Input

Figure-5.10 VOR–Rx system [K3-15]

N

TO VOR-Tx

TO

E

W

112 → 118 MHz

AM Detector

FR

S

Rx

Figure-5.11 CDI [K6-15]

57

1 dot = 2o FROM VOR-Tx

∝Voltage output

Chapter 5: Short-Range NAVAIDS 9,960 Hz

Amplitude

R @ Rx

A t any radial it will be the same

10,440 Hz

E

9,960 Hz

10,440 Hz

S

W

N

P = 00

V &R

Amplitude

V @ Rx

9,480 Hz

Time

N

Radial: 0000 or 3600

M. Abdulla

Time

E

S

W

N

Amplitude

V @ Rx

Radial: 2700

Dipole

N

P = 2700

R

Time

V

S

W

N

E

Dipole

E

Figure-5.12 Examples of signals observed by the VOR-Rx at different radials [K3-16]

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•

Advantage: VOR is more efficient than ADF since its indicator point to the GND VOR-Tx. Whereas ADF provides a relative bearing corresponding to the offset between the A/C longitudinal axis and the NDB, and hence does not point to the GND base beacon.

•

Disadvantages: 1) Error § ± 2° 2) Limited to LOS due to VHF band operation 3) VOR signals are either reflected or blocked or distorted due to: ™Buildings ™Mountains ™Fences ™Power Lines ™Etc. 4) At high ALT interference may occur between 2 GND stations operated at the same frequency. 5) VOR does not provide the A/C HDG, it only points to the GND station.

•

Future: GPS is more accurate and efficient than VOR; however, VOR technology should still be used in A/C as a backup NAVAID in case a SAT communication problem occurs.

5.3 Distance Measuring Equipment – DME •

Principle: Provides distance between A/C and GND station. Ideally what we want from the DME system is the separation between the A/C and the DME station measured over GND (D); however, the DME usually outputs the slant distance (S) 25.

D

n ce a t is

DME

Figure-5.13 Example illustrating the DME principle

25

For a graphical understanding of D and S refer to Figure-5.17.

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On the GND: 1) Rx-Tx26: DME or NDB-DME or VOR-DME or TACAN or VORTAC systems. 2) Frequency: UHF § 960 – 1215 MHz ™Number of Channels: 100 3) Each GND station is able to handle 100 A/Cs simultaneously.

Freq = f 1

Freq = f 1 ± 63 MHz

Rx

Tx

50 µ sec Delay

Figure-5.14 DME GND station left:[K3-17] right:[K4-5]

DME (Rx-Tx / UHF) VOR (Tx / VHF)

Figure-5.15 VOR-DME GND station left:[K4-6] right:[K5-1]

•

In the A/C: 1) Rx-Tx: DME system also known as (a.k.a) the Interrogator. 2) Frequency: UHF

26

Note that the DME system is different from ADF and VOR technologies, in the sense that the GND system is not only a Tx but also a Rx. Hence deducing from that, the airborne DME will also be a Rx-Tx system.

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3) Range of Operation: 150 – 200 miles § 240 – 320 km 4) A/C DME displays: ™Distance in: nm ™GS in: kts ™Remaining time to get to GND station in: minutes

Interrogator Calculate distance

Ranging Circuits

Tx

Distance

Rx

Freq = f 1 Freq = f 1 ± 63 MHz

Figure-5.16 DME airborne system [K3-17]

•

Functionality: 1) A/C DME Interrogator: ™Interrogator transmit a signal27 on one of the channels at: Freq = f1 2) DME GND Station: ™GND station receives the signal. ™Add a delay of 50 ȝsec to the signal ™Signal is then transmitted to the A/C at: Freq = f1 ± 63 MHz 3) A/C DME Interrogator: ™Interrogator receives the signal ™Measures the actual time that the signal traveled: Time = ¨T – 50 ȝsec ™Calculates the distance using the following correspondence: 1 nm Ł 12 ȝsec

•

Advantage: DME is rarely affected by precipitation static and thunderstorms.

•

Disadvantages: 1) Slant Error: We use DME for the purpose of getting the distance D; however, the system will provide us the slant distance S. To overcome this inconvenience, we will show below that the larger S is w.r.t. the A/C ALT A, the smaller the Error.

27

Each A/C transmits a signal with a specific pulse rate (Freq) and pattern.

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A : A/C Altitude D : Ground Distance S : Slant Distance

S

A

D

DME

Figure-5.17 DME slant error

™If S >> A, then D § S. 1:

If: S  A or S 2  A 2

2 : S 2 = A 2 + D 2 or D = S 2 − A 2 ≈ S 2 = S 3: Then: D ≈ S

(5.4)

™If S = 5A, then Error § 2%. Also, If S > 5A, then Error < 2%. 1:

If: S = 5A

2:

D = S 2 − A 2 = 25A 2 − A 2 = 24A 2 ≈ 4.9A

3 : Error = 4:

estimate − real S −D 5A − 4.9A × 100 = × 100 ≈ ×100 = 2.041% ≈ 2% (5.5) 4.9A real D Then: Error ≈ 2%

™If S = A, then Error = 100%28. 1:

If: S = A

2:

D = S 2 −A2 = A2 −A2 = 0

3 : Error = 4:

estimate − real S −D A −0 × 100 = × 100 ≈ × 100 = ∞ = 100% 0 real D Then: Error ≈ 100%

(5.6)

S=A

D=0 DME

Figure-5.18 Greatest DME slant error 28

When the A/C is above the DME GND station we expect to have a null reading; however, the A/C DME display will output the ALT.

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2) Limited to LOS due to UHF band operation

•

Future: GPS is more accurate and efficient than DME; however, DME technology should still be used in A/C as a backup NAVAID in case a SAT communication problem occurs.

5.4 Tactical Air Navigation – TACAN •

Principle: Provides A/C bearing and distance w.r.t. a GND station for MIL purposes. The bearing part of this system is similar to VOR, but quite unique for the nature of MIL operation. As for the distance measurement capability, it is in fact obtained through the integrated DME system within the TACAN GND station.

•

On the GND: 1) Rx-Tx: TACAN or VORTAC systems. 2) Frequency: UHF § 960 – 1215 MHz ™Number of Channels: 252

Figure-5.19 TACAN GND station [K4-7]

•

In the A/C: 1) Rx-Tx: TACAN system. 2) Frequency: UHF 3) Range of Operation: 200 miles § 320 km

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Advantages: 1) Rejects bounced signals 2) Low power consumption 3) Resistant to: ™Shock ™Vibration ™Electro-magnetic Interference (EMI) 4) Flawless in the world’s most environmentally severe sites: ™Snow ™Humidity ™Rain ™Fungus ™Sand ™Dust 5) Maintenance free antennas, since it has no moving parts. 6) Combines bearing and distance capabilities together. 7) If the bearing Tx becomes defective, the facility will remain active as a DME GND station.

•

Disadvantages: 1) Bearing Error < ± 3.5° 2) Distance Slant Error 3) Limited to LOS due to UHF band operation.

•

Future: GPS is more accurate than TACAN; however, TACAN technology is a stable MIL NAVAID and should remain in operation for the years to come.

5.5 VOR and TACAN – VORTAC •

Principle: GND system with both VOR and TACAN for bearing and distance purposes. In a broader sense, instead of having VOR, and TACAN GND stations separately, we could simply join them into a single GND station known as VORTAC.

•

On the GND: 1) Rx-Tx: VORTAC system. 2) Frequency: ™VHF § 108 – 118 MHz (VOR) ™UHF § 960 – 1215 MHz (TACAN which has an integrated or built-in DME)

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TACAN Bearing

TACAN (Rx-Tx / UHF) Civilian A/C DME

Distance

VOR

Bearing

VOR (Tx / VHF)

Figure-5.20 VORTAC GND station left:[K4-8] right:[K3-18]

•

In the A/C29: 1) CIV A/C: ™Rx: VOR-Rx system. ™Rx-Tx: DME Interrogator. 2) MIL A/C: ™Rx-Tx: TACAN system.

•

Advantage: 1) Combining GND stations for CIV and MIL is quite feasible in terms of: ™Cost ™Operations ™Maintenance 2) Other advantages enumerated for VOR30 and TACAN31 are also present here.

•

Disadvantages: The same disadvantages enumerated for VOR30 and TACAN31 are also present here.

•

Future: GPS is more accurate than VORTAC; however, VORTAC technology is an optimized approach for a NAVAID GND station, and hence should remain in operation.

29

VORTAC is a GND station. But to take advantage of this station different equipments are needed within the A/C depending if the vehicle is used for CIV or MIL purposes. 30 For VOR advantage and disadvantages refer to Page-59. 31 For TACAN advantages and disadvantages refer to Page-64.

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5.6 Random or Area Navigation – RNAV •

Principle: Provides A/C bearing and distance w.r.t. a 3D artificial reference point known as Waypoint32 (WPT). In fact, the main motivation to navigate using computerized WPTs is to obtain optimized air routes from departure to arrival. VORTAC-3

VORTAC-1

Arrival

WPT-3 WPT-2

Departure

WPT-1 VORTAC-2

Figure-5.21 Example illustrating the RNAV principle using VORTAC GND stations [K6-16]

•

Position Fix: To obtain WPTs, we need to have the present A/C 3D33 position fix. There are 3 general ways to do that using either: 1) GND Stations and A/C Radar:

™GND Stations: VOR-DME or VORTAC to obtain bearing and distance; which could eventually be transformed to A/C LAT and LON. ™A/C Radar: Radio Altimeter (RA) to obtain the A/C ALT. 2) A/C Self-Contained Systems: INS or DNS34 3) Orbital SAT System: GPS34

•

In the A/C: Airborne RNAV System performs 2 important tasks: 1) Identifies WPT needed: RNAV calculates WPTs or uses already loaded WPTs from a NAV Database (DB) based on the present A/C position and the flight plan required to reach destination. 2) Outputs relative A/C position: Once the WPT is identified in 3D, then the A/C bearing and distance is obtained w.r.t. it. Now, the A/C simply needs to fly toward that WPT.

32

WPT could also be thought as a 3D point where we want the A/C to be after some time has elapsed. 3D represents the LAT, LON, and ALT of the A/C. 34 INS, DNS, and GPS are systems that provide continuous A/C 3D position fixes; they will be explained later in this chapter. 33

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RNAV System A/C 3D Position Fix

Compute WPTs

Flight Plan NAV DB

A/C Bearing w.r.t. a WPT A/C Distance w.r.t. a WPT

Figure-5.22 RNAV airborne system

3) Secondary Outputs: Some RNAV systems also outputs:

™Estimated Time of Arrival (ETA) to next WPT ™Necessary IAS required to achieve ETA ™Estimated fuel remaining at destination •

Advantages: 1) More direct, efficient, and flexible routes are generated. 2) Arrive faster at destination (i.e. time effective). 3) Requires less fuel to reach destination (i.e. cost effective). 4) More disperse NAV (i.e. full use of airspace). 5) More traffic is possible at random locations; hence, less traffic is obtained in a specific geographical area.

•

Disadvantages: Major errors are those involved in obtaining the A/C position fix using GND stations. 1) Same errors35 as those of VOR, DME, or VORTAC. 2) A possible way to obtain fictitious WPTs is through corresponding GND stations; however, they are limited by operation range. 3) The airway obtained using RNAV is tighter than the V or J-airway: RNAV-airway width = 8 nm § 15 km V or J-airway width = 10 sm § 16 km

•

35

(5.7) (5.8)

Future: It is quite evident that INS or DNS or GPS facilitates the use of RNAV in oceanic airspace since no stations are needed. Also, GPS is a more accurate way to obtain A/C position fix as opposed to other methods; and therefore, the use of GPS should make the GND station technology retire in the years to come. Most important errors are those of signal reflection of VOR radials and slant error involved in the DME process.

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5.7 Combined Displays Several instruments are combined together to facilitate pilot-A/C interface, and hence lower the crew workload.

5.7.1 Radio Magnetic Indicator – RMI •

Indicator Characteristics: 1) 2) 3) 4)

Flux-valve compass card that indicates the A/C magnetic HDG. A needle driven by ADF-Rx indicating the NDB36 magnetic bearing w.r.t. A/C. A needle driven by VOR-Rx indicating the VOR GND station bearing (TO) w.r.t. A/C. If we extend the bearing lines of the 2 GND stations we obtain the position fix of the A/C.

Figure-5.23 RMI left:[K5-2]

5.7.2 Horizontal Situation Indicator – HSI •

Indicator Characteristics: 1) 2) 3) 4) 5)

DG37 to indicate A/C HDG. Warning flags to indicate loss or unreliable information. Manually adjust to desired A/C HDG. Manually adjust to a tuned GND station. Vertical and horizontal guidance during the Approach/Landing phase.

36

Using ADF functionality from the RMI simplifies NAV, since we will obtain the NDB magnetic bearing and not the ADF relative bearing as explained on Page-51. 37 To read more on DG refer to Page-33.

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A/C HDG Compass Warning Flag NAV Warning Flag

DG information is invalid

indicate loss of NAV signal

GS0 Deviation

VOR/LOC Deviation

Vertical guidance during landing

VOR or horizontal guidance during landing

Course Select

HDG Select

pointing "TO" a tuned GND VOR or NDB station or even a LOC during approach

pointing to desired A/C HDG Glideslope (GS0) Localizer (LOC)

Figure-5.24 HSI [K5-3]

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Chapter 6 Long-Range NAVAIDS

Knowledge is of two kinds. We know a Subject ourselves, or we know where we can find information upon it. — Samuel Johnson

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6.1 Long Range Navigation (revision-C) – LORAN-C •

Principle: Provides A/C position fix (2D)38. In fact, this technology is known as a hyperbolic system since it determines NAV fix using hyperboles or parabolic lines (black) generated from the intersection of signals (blue & red) radiated by GND stations. Also, notice the formation of some straight lines (green).

Figure-6.1 Formation of the hyperbolic grid [K6-17]

•

Position Fix: To obtain the A/C position fix at least 2 hyperbolic grids are required. This means that at least 2 Line Of Position (LOP) have to be generated from a single master station, and at least 2-slave GND stations. Master GND Station

LOP-B

LOP-A

B Slave GND Station

A Slave GND Station LORAN-C-Rx System

Figure-6.2 Position fix using LORAN-C system [K6-18] 38

2D represents the LAT, and LON of the A/C.

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On the GND: 1) Tx: Master & Salve LORAN-C-Tx systems. 2) Frequency: LF § 90 – 110 kHz 3) LORAN-C signal pulses propagate using GND waves. 4) Possible Tx topologies: ™Trial: 1-master and 2-slave stations. ™Star: 1-master and 3-salve stations. ™Square: 1-master and 4-salve stations. 5) The master station transmits a sequence of 9-pulses. 6) After a delay39, the slave station will also emit a sequence of 8-pulses.

1350 ft ≈ 0.4 km

600 − 800 m iles apart 970 − 1290 km apart

Figure-6.3 LORAN-C GND stations left:[K4-9]

•

In the A/C: 1) Rx: LORAN-C-Rx system. 2) Frequency: LF 3) Highly selective Rx in order to avoid interference from other signals. 4) When the 9-pulses from the master station reaches the A/C, the Rx will start counting the time (¨t) it takes for the slave 8-pulse signals to reach the airborne Rx. 5) To calculate the A/C position fix, we need to know the position of the master and slave stations, the station separation distance, and ¨t.

39

Note that the delay introduced here is dependent on the separation distance between the specific master-slave pair stations.

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Position of GND stations

LORAN-C Rx Processor

∆t

A/C LAT A/C LON

Stations seperation distance

Figure-6.4 LORAN-C airborne processor

6) There exist Rx with dual LORAN-C and GPS usage. The processor within this Rx will calculate and output: ™A/C Position: LAT & LON ™GS ™Wind Drift ™WPT information ™ETAs ™Airport data ™Etc.

•

Advantages: 1) LORAN-C does not suffer from LOS since it operates at LF band. 2) Hyperbolic grid NAV provides a more direct route similar to WPT NAV. 3) Signal propagation is based on GND waves; therefore large travel ranges40 are possible.

•

Disadvantages: 1) Error § ± 150 m 2) Ground Wave Propagation Error: The velocity at which the signal travels may vary, and hence some offset may be introduced in calculating the A/C position fix. 3) There are not enough LORAN-C GND stations in the world to cover all possible air routes.

•

Future: GPS should make LORAN-C technology retire.

6.2 Optimized Method for Estimated Guidance Accuracy – OMEGA •

40

Principle: Provides A/C position fix (2D). This technology is based on NAV using a hyperbolic grid, which is quite similar to the LORAN-C.

NAV ranges in the 1000’s of miles § 1600 km

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•

Position Fix: To obtain the A/C position fix at least 2 LOPs are required as shown in Figure-6.2 above. The only difference is that in the OMEGA process we need 3 GND stations without tagging them as master or salve like we did using LORAN-C.

•

On the GND: 1) Tx: Only 8 OMEGA-Tx systems exist in the world. 2) Frequency: VLF § 10.2 – 13.6 kHz 3) OMEGA signals propagate using sky waves. 4) Each GND station could transmit 4 possible time-shared signals41 (10.2, 13.6, 11.33, or 11.05 kHz). 5) In addition to the signals above a unique ID signal is emitted from each station. ™Norway / Aldra: 12.1 kHz ™Liberia / Monrovia: 12.0 kHz ™US / Hawaii / Haiku: 11.8 kHz ™US / North Dakota / La Moure: 13.1 kHz ™France / Réunion: 12.3 kHz ™Argentina / Golfo Nuevo: 12.9 kHz ™Australia: 13.0 kHz ™Japan / Tsushima: 12.8 kHz 6) Transition-time from one signal Freq to another § 0.2 seconds. 7) The signal transmission scheme repeats every 10 seconds. 8) GND based atomic clocks are used to synchronize stations among each other.

10 Seconds

LOCATION

0.9

Norway Liberia US / Hawaii US / North Dakota France / Réunion Argentina Australia Japan

10.2 12.0 11.8 11.05 12.3 12.9 11.33 13.6

0.2

1.0

13.6 10.2 11.8 13.1 11.05 12.9 13.0 11.33

0.2

1.1

0.2

11.33 13.6 10.2 13.1 12.3 11.05 13.0 12.8

1.2

12.1 11.33 13.6 10.2 12.3 12.9 11.05 12.8

0.2

1.1

12.1 12.0 11.33 13.6 10.2 12.9 13.0 11.05

0.2

0.9

11.05 12.0 11.8 11.33 13.6 10.2 13.0 12.8

0.2

1.2

12.1 11.05 11.8 13.1 11.33 13.6 10.2 12.8

0.2

1.0

0.2

12.1 12.0 11.05 13.1 12.3 11.33 13.6 10.2

Figure-6.5 Time-frequency transmission scheme for OMEGA GND stations [K6-19] 41

The 8 worldwide GND Tx stations are time-frequency multiplexed. In other words, if one of the 8 possible GND stations transmits a signal with a specific frequency at a given time, then none of the other remaining 7 stations can transmit a signal with that frequency at that moment as in Figure-6.5.

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US / North Dakota Japan US / Hawaii Liberia

France / Réunion

Australia

Argentina

Figure-6.6 Location of the OMEGA GND Tx stations [K6-19]

•

In the A/C: 1) 2) 3) 4)

•

Rx: OMEGA-Rx system. Frequency: VLF Range42 of Operation: 6,000 miles § 10,000 km 43 Highly selective Rx in order to avoid interference from other signals.

Advantages: 1) OMEGA does not suffer from LOS since it operates at VLF band. 2) Hyperbolic grid NAV provides a more direct route similar to WPT NAV. 3) Sky wave propagation uses the reflective property of the ionosphere layer; hence large travel ranges are possible.

•

Disadvantages: 1) Error § ± 0.5 miles § ± 1 km 2) Sky Wave Propagation Error: The velocity at which the signal travels may vary, and hence some offset may be introduced. 3) Diurnal Error: The ionosphere layer varies in height44 during day and night and therefore errors are generated. That is, for position fix 3-stations are needed, and in most cases these GND stations are not aligned within the same time zone; therefore different ionosphere heights will result at different geographical locations. 4) Maintenance of the OMEGA GND stations is quite costly.

42

The large range of operation explains why only 8-GND stations are required to have a worldwide coverage. To get a sense of what 10,000 km is, think of it as going from Montréal to Vancouver and back to Montréal. 44 For more on the effect of daytime / nighttime on the ionosphere layer refer to Page-44. 43

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Future: GPS made the OMEGA retire on September-30-1997. However, The North Dakota station is still used by the US Navy for VLF submarine communications.

6.3 Inertial Navigation System or Inertial Reference System – INS or IRS •

Principle: Provides A/C velocity (3D) and position fix (3D). In fact, INS is based on DR45, i.e. we G first need to obtain the A/C vectorial acceleration ( a ), then integrate (œ) once to obtain the velocity, and finally integrate a second time to get the position. Also, what makes this technology quite amazing is that it is a self-contained system; hence, no GND stations are required for operation. Automatic Breaking System (ABS) Flight Management System (FMS) Initial Position (3D)

Air Data Computer (ADC)

INS

Acceleration (3D)

3D Position Fix Velocity Acceleration Attitude True/Magnetic HDG ALT TAS

Flight Control Computer (FCC)

DNS

Black Box

GPS

Weather Radar System (WXR) ETC ...

Figure-6.7 Airborne INS interfaces

•

In the A/C: There are 2-types of INS: 1) Stable-Platform INS or Gimballed INS:

™The stable-platform isolates the gyroscopes and accelerometers from the A/C angular motion, and hence remains in-synch with the earth coordinate system. ™Contains 3 Gyroscopes (G): ¾GROLL ¾GPITCH ¾GYAW ™Contains 3 movable Accelerometers (A): ¾ALAT = AN-S ¾ALON = AW-E ¾AALT 45

For more on DR refer to Page-3.

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ALAT ALON

³³

A/C LAT A/C LON

Initial Position (2D)

AALT

³³

A/C ALT

Altimeter

Figure-6.8 Stable-platform INS left:[K4-10] A/C HDG

ALAT = AN-S

N

ALON = AW-E

W

E Stable Platform

S

Figure-6.9 2D-view of a stable-platform INS [K3-19]

Yaw Axis Roll Axis (Inner) Pitch Axis Roll Axis (Outer)

Motor Vehicle

3 Accelerometers and 3 Gyroscopes

Gimbal Ring

Figure-6.10 3D-view of a stable-platform INS [K3-20]

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2) Strap-Down INS:

™This type of INS has no moving parts; and therefore, the accelerometers are solidly connected46 to the airframe and gyroscopes are well aligned with the A/C X-Y-Z coordinate47 system. ™Contains 3 laser gyroscopes: ¾GROLL = GX ¾GPITCH = GY ¾GYAW = GZ ™Laser gyroscope: ¾2-laser light beams are sent one clockwise, and the other counter-clockwise. ¾Doppler Effect: Beam going against the rotation produces high Freq. ¾Therefore we want to determine: ¨f = Freq difference of the two light beams. ¾If ¨f = 0: then the fringing pattern is stationary and there is no angular rotation in the Z-axis. ¾If ¨f  0: then the fringing pattern moves at a rate ∝ ¨f ∝ angular input rate. Photodiodes Prism Fringing Pattern Mirror

Clockwise Laser Beam

Counter-Clockwise Laser Beam

Z-axis Angular Input Rate

Mirror

Figure-6.11 Laser gyroscope used by the strap-down INS left:[K4-10] right:[K6-20]

46 47

To have accelerometers connected firmly to the airframe is advantageous since it eliminates dynamic errors. For more on the A/C coordinate system refer to Pages-25 & 26.

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™Contains 3 non-movable accelerometers: ¾AX ¾AY ¾AZ 3) In addition to velocity and position, INS also provides:

™TK to fly ™Off-track distance ™Distance between 2 points ™Stores alternate destination positions ™Determines true North direction ™Recalculates ETAs •

Advantages: 1) In General: ™INS is a self-contained airborne system that does not need any outside NAV source.

™Displays in real-time the A/C velocity and position. ™Operate at all ALT48. ™Sometimes GPS is used as an aid to INS in order to correct or attenuate errors. 2) Stable-Platform INS: ™Aligned with the earth coordinate system despite A/C angular motion.

™Accelerometers and gyros are protected from malfunctioning dude to severe maneuvers since they are not directly connected to the airframe. 3) Strap-Down INS: ™Mechanically simple to realize.

™Laser gyros are more robust than traditional ones. •

Disadvantages: 1) In General: ™Drift Error49 § ± 0.5 kts § ± 1 km/hr

™Accuracy of velocity and position degrade50 w.r.t. time.

48

Since INS does not depend on GND stations it could operate at all possible ALTs. It’s not limited by height. This error is valid provided no GPS support is available to the INS. In fact, the error is mostly manifested due to the gyro and the integrator used within the INS system. 50 This is quite obvious since after all INS is a self-contained DR system; i.e. it always depends on the previous result. 49

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™Computational errors: ¾Round-off and truncation ¾Approximation used to simplify calculation algorithms ™Errors generated by non-orthogonality of accelerometers. ™Vibration and thermal variation may cause flaws in information data. ™INS is an expensive51 technology. 2) Stable-Platform INS: ™Mechanically more complicated to realize.

™Errors generated by non-orthogonality of gyros. ™Gyros may suffer from EMI. 3) Strap-Down INS: ™NAV accuracy is highly dependant on the A/C maneuver, given that the accelerometers and gyros are directly connected to the airframe.

™Computationally demanding: G ¾Convert a from A/C coordinates to earth coordinates. ¾Then perform DR to get velocity and position.

Strap-Down Computation Sequence Stable-Platform Computation Sequence

K a

ª AX º « » A/C Coordinate = « AY » «¬ AZ »¼

Using Rotation Matrix

K a

ª ALAT º « » Earth Coordinate = « ALON » «¬ AALT »¼ K Velocity = ³ a (t ) dt

G Position = ³ v (t ) dt

Figure-6.12 Computation sequence in stable-platform and strap-down INS

•

51

Future: The combination of INS and GPS is great since one completes the other. In other words, GPS can calibrate the INS drift error, while INS attitude data can aid GPS. Prices vary from $50,000 to $120,000 US.

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6.4 Doppler Navigation System – DNS •

Principle: Provides A/C velocity (3D) and position fix (3D). This system is primarily used for MIL purposes requiring high-speed low-altitude flights. First, the A/C velocity is obtained using the Doppler radar, then the information is inputted52 to a NAV computer so that the position fix can be calculated. Also, similar to INS, this technology is a self-contained DR system and therefore, does not depend on any outside source.

DNS Velocity (3D)

ª Roll º Attitude = « » ¬ Pitch ¼

Doppler Radar

³

Position Fix (3D) Bearing to next WPT Distances to Next WPT

HDG Initial Position (3D) Figure-6.13 DNS

•

In the A/C: 1) Tx-Rx: DNS radar system. 2) Frequency: SHF ™In precipitations: 8.8 – 9.8 GHz ™Otherwise: 13.25 – 13.40 GHz 3) A/C Doppler radar transmits53 a beam to GND. 4) The beam is reflected and observed at the A/C Rx with velocity information. 5) Velocity is then integrated to obtain position.

VH = GS

I

γ

Tx-Rx Doppler Radar

VR

γ

VH

VR /2

Figure-6.14 Example illustrating calculation of GS using DNS provided A/C is flying straight [K3-21]

VH : A/C Horizontal Velocity Component (i.e. GS) [ m/s ] . VR :

ν: γ: 52 53

Relative Velocity Between Tx-Rx [ m/s ] .

Doppler Frequency Shift [ Hz ] . Angle between VH and Beam [ degrees ] .

Speed of Light ª¬3 × 108 m/s º¼ . λ : Wavelength of Transmitted Beam [ m ]. c:

f : Frequency of Transmitted Beam [ Hz ] .

Notice that the HDG, which is provided either by a magnetic compass or a gyro, is also feed to the integrator. In fact, there should be a minimum of 3 beams that are transmitted in order to observe a 3D velocity and position fix.

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1:

c = λ f or λ =

2:

VR = λν =

c f

cν f

3: cos ( γ ) =

adj VR / 2 VR cν = = or VR = 2VH cos ( γ ) = 2VH hyp VH f

4:

=

VH

m/s

3 × 108ν 1.5 × 108ν cν = = [ m/s] 2 f cos ( γ ) 2 f cos ( γ ) f cos ( γ )

(6.1)

1[ km ] = 1000 [ m ] 1[ hr ] = 3600 [s ]

5:

3.6 [ kts ] = 1.944 [ kts ] 1.852 1.5 × 108 × 3.6ν 5.4 × 108ν = = [ km/hr ] f cos ( γ ) f cos ( γ )

1[ m/s ] = 3.6 [ km/hr ] = VH

km/hr

6: VH •

kts

1.5 × 108 × 1.944ν 2.916 × 108ν = = [ kts ] f cos ( γ ) f cos ( γ )

Advantages: 1) DNS is a self-contained airborne system that does not need any outside NAV source. 2) DNS operates over land and water. 3) Average velocity information is extremely accurate. 4) A/C Tx-Rx is light, small, and cheap since it requires a small amount of power for operation. 5) Sometimes a combination of INS-DNS is used to obtain more accurate readings since one technology could correct the other due to the fact that: ™INS will generate a short-term velocity error ™DNS will generate a long-term velocity error

•

Disadvantages: 1) Errors: ™GS Error § 0.25% § ± 0.0025 × VH kts ™DA Error § 0.25% § ± 0.0025 × į degrees ™Overall54 System Error § 0.50% 2) 3D velocities are first obtained in A/C coordinates and then transformed to earth coordinate and therefore calculation errors will be present.

54

Here we take into account all possible sources of error including HDG error.

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3) DNS performance is diminished in extreme conditions of rain. 4) While operation over water, accuracy is degraded due to: ™Water motion ™Complete smoothness of water surface •

Future: GPS is more accurate than DNS; however, DNS should remain in operation for special MIL applications.

6.5 Global Positioning System – GPS •

Principle: Provides A/C position fix (3D). This technology is without any dought the most precise system used in NAV by CIV and MIL A/C. To understand why, we first need to realize that generally there exist a tradeoff between position fix accuracy and the coverage area in systems seen thus far. In other words, we cannot have the best of both worlds. However, we know for a fact that SATs operate at the UHF band (i.e. high Freq), and hence accurate position fix reading. As for ensuring a large and excellent coverage area we must place the GPS Transponder (i.e. SAT) faraway in outer space at roughly 20,000 km form the earth surface, and not on the GND. As a result, GPS55 becomes an exceptional NAV tool ever invented due primarily to its accurate position fix and large coverage area.

Frequency Position Fix Coverage Area Large Low (e.g. OMEGA) Not Accurate Accurate Small High (e.g. VOR) Figure-6.15 General tradeoff that exists between NAVAID systems

•

Timeline: 1) 1963: The concept of GPS is born in a project study by Dr. Ivan Getting of The Aerospace Corporation and Col. Dr. Brad Parkinson of the US Air Force. 2) 1971: The L2 frequency concept is added to the GPS project to aid in the correction brought by the ionosphere layer variation. 3) 1973-12-17: Proposal for the GPS is approved by the Defense System Acquisition and Review Council (DSARC). 4) 1974-06: Rockwell International56 is selected as the SAT contractor for the GPS program. 5) 1978-02-22: First GPS SAT is launched by the US DoD for MIL use.

55

GPS was initially known as Navigation System with Timing And Ranging (NAVSTAR) by the US Department of Defense (DoD). Since NAVSTAR and GPS are similar terms, they could be used interchangeably. 56 In December-1996 Rockwell International was acquired by Boeing.

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6) 1981-12-18: Block-I SAT is lost due to a launch failure. 7) 1983-09-16: US President Ronald Reagan declassifies GPS from purely MIL to being a public project. This decision was made because the Soviet Union shot down a CIV Korean A/C after accidentally entering into Soviet airspace on 1983-09-01. 8) 1986-01-28: Space shuttle Challenger explodes during launch. This caused a 2-year delay in the deployment of Block-II GPS, since this vehicle was planned to transport SATs to outer space. 9) 1989-02: US Coast Guard57, part of the Department of Transportation (DoT), assumes full responsibility of the GPS program for CIV use. 10) 1990-03-25: DoD deliberately activates the Selective Availability (SA) in order to degrade the position accuracy for CIV GPS w.r.t. MIL. 11) 1990-08: GPS SA is turned off during the Persian Gulf War since not enough P(Y) Rx were available; MIL personnel had no choice but to use CIV GPS Rx. All together 9,000 GPS Rx were used during Operation Desert Storm. 12) 1991-07-01: SA is reactivated after the end of the Persian Gulf War. 13) 1991-09-05: US decided to make GPS available to the international community free of charge upon its completion. 14) 1995-04-27: US Air Force Space Command (USAFSC) declares the 24 SAT GPS constellation fully operational. 15) 1997-01-17: The First of the Block-IIR SATs is lost due to a launch failure. 16) 2000-05-01: SA is turned off due to a presidential directive by US president Bill Clinton58 signed in March-1996. Accuracy changed from 100 m to 10 – 15 m for CIVs. •

Position Fix: To obtain a 2D position fix we need at least 3 SATs. Whereas for a 3D fix a minimum of 4 SATs are required. Logically speaking, this does not make any sense59 because it goes without saying that for a least position fix calculation, the size of the dimension and SAT must be equal. Technically speaking, that is right; however, from a practical or cost effective approach we will always require an extra SAT. The reasoning below will help us understand why:

Number of Satellites = Number of Dimensions + 1

(6.2)

1) SAT operate at the UHF band ∴ Signal is an LOS Wave ∴ Wave travels at the speed of light 57

US Coast Guard Navigation Center: www.navcen.uscg.gov Statement by US President Bill Clinton on setting SA to zero: www.ostp.gov/html/0053_2.html 59 It would make some sense from a redundancy perspective, but not otherwise. 58

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2) Speed of light = c = 3 × 108 = 0.3 × 109 = 0.3 / 10-9 [m/s] = 0.3 [m/nsec] 3) From the speed of light transformation above, we obtain the following important correspondence60:

Ł

{ Timing Error = ± 1 [nsec] }

{ Position Fix Error = ± 0.3 [m] }

(6.3)

4) All this, to say that we need powerful clocks to measure the time61 that it takes for a signal to go from the SAT to the GPS-Rx. 5) The most precise clocks available today are known as atomic clocks62. They exist in 2 types with clock frequency of 10.23 MHz63:

™Cesium (Cs) Atomic Clock: ¾Error Rate: 1 [sec] every 1,000,000 [years] Ł 0.000 001 [sec/year] ¾Price: $25,000 – $50,000 US ™Rubidium (Rb) Atomic Clock: ¾Error Rate: 1 [sec] every 1,000 [years] Ł 0.001 [sec/year] ¾Price: $1,000 – $1,500 US 6) To measure the time the signal travels from SAT to Rx would mean that each of these HW must be equipped with an atomic clock. In fact, all GPS SAT have Cs and/or Rb clocks; however, most GPS-Rx have an ordinary quartz timer due to its low-cost w.r.t. an atomic clock. Hence, the measured signal time would not be as accurate as desired, which eventually maps to a vague position fix. i:

Satellite Number.

c:

Speed of light ª¬ c=3 × 108 m/s º¼ . Accurate time it take a signal to travel from SAT to the GPS-Rx [sec] .

Ti : Ti :

Inaccurate time it take a signal to travel from SAT to the GPS-Rx [sec] .

∆T : Time factor of inaccuracy [sec ] . Ri : Ri :

Accurate range between SAT and the GPS-Rx [ m ] .

Inaccurate range between SAT and the GPS-Rx [ m ] .

∆R : Range factor of inaccuracy [ m ] . 60

Correspondence [Ł or ļ] is not the same thing as equivalence [=]; correspondence is derived from a ratio as in the case of the speed of light. 61 SATs time are regulated and synchronized by the US Naval Observatory (USNO) master clock located in Washington D.C.: http://tycho.usno.navy.mil/cgi-bin/anim 62 The name atomic clock could be misleading, in the sense that me might think that it uses atomic or nuclear energy or that it is radioactive; it’s actually far from that. Atomic clocks, as in traditional clocks, keep track of time through oscillation generated by a mass-spring model system. The major difference here is that oscillation occurs between the nucleus [proton: positive charge | neutron: no charge] of an atom and the surrounding electrons [negative charge]. 63 We need to realize here that a SAT clock would appear to run faster by a factor of 38 ȝsec / day w.r.t. a clock on earth even if they were initially synchronized. This effect is in principle due to Albert Einstein theory of relativity known as time dilation. Therefore, to make the SAT clock appear to run at the same rate as the one on earth an offset is introduced to the SAT clock: 10.23 – 0.000 000 004 57 = 10.229 999 995 43 MHz.

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X S -i : YS -i :

Satellite X-axis component [ m ] . Satellite Y-axis component [ m ] .

ZA/C :

A/C Z-axis component [ m ] .

Z S -i : Satellite Z-axis component [ m ] . X A / C : A/C X-axis component [ m ]. YA / C : A/C Y-axis component [ m ].

Logically speaking 3 SATs are required for a 3D

i = 1, 2, 3

1:

position fix. Measure the time that it takes for a signal to go from a SAT to a GPS-Rx. This measured time is obviously inaccurate

Ti

2:

since the Rx does not have an atomic clock. The measured inaccurate time is for sure greater than the

Ti < Ti ∴ T = T − ∆T

3:

i

actual time by a factor of say ∆T . The actual distance between

i

(

)

Ri = cTi = c Ti − ∆T = cTi − c∆T

the SAT and the observer is nothing else than the

∴ Ri = Ri − ∆R

4:

inaccurate range minus some factor ∆R. We know the SAT position

( X S -i , YS -i , Z S -i ) , we also

X S -i − X A / C

ª X S -i º ª X A / C º « Y » − «Y » « S -i » « A / C » «¬ Z S -i »¼ «¬ Z A / C »¼

know the inaccurate time Ti

= YS -i − Y A / C Z S -i − Z A / C

and the speed of light c. What we want at this moment

=

( X S -i − X A / C )

2

is to get the A/C position,

+ (YS -i − YA / C ) + ( Z S -i − Z A / C ) 2

2

=

5:

However, we have another

Ri = Ri − ∆R = cTi − ∆R

unknown ∆R; this means that the number of unknowns is

∴

( X S -i − X A / C )

2

namely ( X A / C , YA / C , Z A / C ) .

2 + (YS -i − YA / C ) + ( Z S -i − Z A / C ) = cTi − ∆R 2

actually 4 and not 3. To solve for 4 unknowns, we must have 4 equations, i.e. we need data from 4 SATs and not 3. ∴ i = 1, 2, 3, 4

86

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Satellite #1:

( X S -1 − X A / C )

2

+ (YS -1 − YA / C ) + ( Z S -1 − Z A / C ) = cT1 − ∆R

Satellite #2:

( X S -2 − X A / C )

2

2 2 + (YS -2 − YA / C ) + ( Z S -2 − Z A / C ) = cT2 − ∆R

Satellite #3:

2 2 2 ( X S -3 − X A / C ) + (YS -3 − YA / C ) + ( Z S -3 − Z A / C ) = cT3 − ∆R

Satellite #4:

( X S -4 − X A / C )

2

2

2

(6.5)

2 2 + (YS -4 − YA / C ) + ( Z S -4 − Z A / C ) = cT4 − ∆R

Satellite #2 P2 = ( X S 2 , YS 2 , Z S 2 )

Satellite #3 P3 = ( X S 3 , YS 3 , Z S 3 )

Time = T2

Satellite #1 P1 = ( X S 1 , YS 1 , Z S 1 )

Time = T3

Satellite #4 P4 = ( X S 4 , YS 4 , Z S 4 )

Time = T1

Time = T4

­ P1 ° ° P2 ® ° P3 °P ¯ 4

; T1 ½ ° 4-Equations ; T2 °  → { X A / C , YA / C , Z A / C ¾ ; T3 ° 4-Unknowns ; T4 °¿

; ∆R}

Figure-6.16 A/C position fix using GPS [K6-21]

•

Transformation: The Earth Centered Earth Fixed (ECEF) Cartesian coordinate system or {X,Y,Z} explained above is quite useful since it simplifies the position fix calculation. However, it does not give us a sense of where we are geographically w.r.t. earth using familiar terms such as {LAT,LON,ALT} of the geodetic system. Also, as far as the transformation is concerned, it is highly dependent on two constants representing the equatorial (a) and polar (b) radii. Several interpretations of a and b exist; however, the GPS technology uses the World Geodetic System of 1984 (WGS-84) datum as shown below: 87

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a: b:

M. Abdulla

Earth Equatorial Radius (a.k.a. semi-major axis) [ 6,378,137 m ]

Earth Polar Radius (a.k.a. semi-minor axis) [ 6,356,752.3142 m ]

f : Flattening of Ellipsoid ª¬( a − b ) a = 0.003352810664 º¼

First Eccentricity of Ellipsoid ª f ( 2 − f ) = 0.081819190842622 º ¬ ¼ e′ : Second Eccentricity of Ellipsoid ª a 2 − b 2 b = 0.082094437949696 º ¬ ¼

e:

X: Y:

X-axis Component [ m ] Y-axis Component [ m ]

Z: Z-axis Component [ m ] LAT : Latitude [ degrees ] LON : Longitude [ degrees ] ALT : v: P:

Altitude [ m ] Radius of Curvature Temporary storage

θ:

Temporary storage

{X , Y , Z} ĺ {LAT , LON , ALT}64 1:

P=

X 2 +Y2

§ Z ×a· ¸ © P×b ¹ § Z + e′2 b sin 3 (θ ) · 3 : LAT = arctan ¨ ¨ P − e 2 a cos3 (θ ) ¸¸ © ¹ §Y · 4: LON = 2 × arctan ¨ ¸ ©X¹ a 5: v= 1 − e 2 sin 2 ( LAT ) 2:

6:

64

θ = arctan ¨

ALT =

(6.6)

P −v cos ( LAT )

A Matlab code for this transformation is available in Appendix D. Mathematically speaking, this conversion will generate an error in the centimeter range (1 cm = 0.00001 km) provided ALT < 1,000 km. This should not be an issue since typical commercial A/C such as a Boeing-747-400 has a maximum ALT of roughly 12 km.

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{X , Y , Z} ĸ {LAT , LON , ALT}65 a

v=

1:

1 − e sin 2 ( LAT ) 2

2 : X = ( v + ALT ) cos ( LAT ) cos ( LON ) 3 : Y = ( v + ALT ) cos ( LAT ) sin ( LON )

(

(6.7)

)

Z = v (1 − e2 ) + ALT sin ( LAT )

4:

Z-axis Notice that the LAT segment does not coincide at the origin since the earth is not spherical {a = b} but rather ellipsoidal {a > b} with a difference = 21.4 km and therefore the orthogonal to the earth tangent maps here!

P(X , Y , Z) = P(LAT , LON , ALT) ALT Z Greenwich / UK

Prim

eM erid

ian

b

a

Y-axis

LAT North a West

LON

X

Y East

Equator

South X-axis Figure-6.17 Graphical definition of {X,Y,Z} and {LAT,LON,ALT} [K6-22]

65

A Matlab code for this transformation is available in Appendix E.

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On the GND: [a.k.a. Control Segment] 1) Rx-Tx: Monitor Stations, Master control Station, and GND Antennas. 2) Monitor Stations: ™Number worldwide: 6

™Monitor stations receives NAV signals from SATs and then transmits it to the Master control station for processing. 3) Master Control Station: ™Number worldwide: 1

™Once or sometimes twice a day, master control determines any NAV adjustments or updates needed and then forwards it to the GND antennas. ™These updates are for: ¾Orbital info (i.e. SAT location within the orbit) ¾Clock synchronization ¾Status of the ionosphere layer 4) GND Antennas: ™Number worldwide: 4

™Receives updates from the master control station and emits signals to SATs.

GND Facilities NAV Signals "FROM" SAT

Monitor Stations

Master Control Station

GND Antennas

(L-Band @ L1 or L2 or L5)

NAV Signals "TO" SAT (S-Band @ 2227.5 Mhz)

Figure-6.18 GPS GND facilities

LOCATION

Monitor Master Control GND Stations Station Antennas

US / Colorado Springs Schriever Air Force Base US / Florida Cape Canaveral US / Hawaii (Pacific Ocean) US / Kwajalein Atoll (Pacific Ocean) UK / Ascension Island (Atlantic Ocean) UK / Diego Garcia (Indian Ocean)

Figure-6.19 Tabular location of GPS GND stations

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US / Colorado Springs Schriever Air Force Base US / Florida Cape Canaveral US / Hawaii US Kwajalein Atoll UK Ascension Island

UK / Diego Garcia

Master Control Station + Monitor Station Monitor Station + GND Antenna Monitor Station Only

Figure-6.20 Location of GPS GND stations [K6-23]

•

In Space: [a.k.a. Space Segment] 1) Tx-Rx: GPS-SAT systems. 2) Frequency: UHF

™L-Band § 500 – 2000 MHz: This band is used in GPS SAT communications. ™L1 = 1575.42 MHz: This Freq is available to CIVs using Course Acquisition (C/A) modulation. It is also available to MIL Rx in two coding known as Precise-Encrypted (P(Y)) and Military-Encrypted (M) modulations. Essentially, the M-code offers a better jamming resistance from enemy w.r.t. P(Y)-code. ™L2 = 1227.60 MHz: This Freq is also available to CIV and MIL Rxs primarily to increase position fix accuracy, to remove errors caused by layer variation of the ionosphere, and to act as a backup frequency. ™L5 = 1176.45 MHz: This Freq is expected to be in action sometime in 2007. It is specifically reserved for CIV use in the field of commercial aviation with improved accuracy. ™L3 = 1381.05 MHz: This Freq is used by the US DoD for detecting missiles, rockets, nuclear detonations, and other high energy infrared events. ™L4 = 1841.40 MHz: This Freq is understudy for future improvement of GPS.

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MIL

CIV

Signal Frequencies Carrier Frequencies Code Names 1.023 MHz 10.23 MHz L1 = 1575.42 MHz L2 = 1227.60 MHz L5 = 1176.45 MHz C/A L2C L5C P(Y) M Figure-6.21 GPS frequencies66 [K6-24]

3) Orbitals67: ™Planes = 6 ™Inclination = 550 ™Number of Active SATs per Plane = 4 4) Position: ™SATs ALT above the earth surface = 10,988 nm § 20,350 km ™The position of each SAT is predefined and known w.r.t. time such that a minimum of 5 SATs are in view at all times. 5) Speed: ™Period68 = 12 hrs ™Average SAT Velocity § 11,265 km/hr 6) Power: ™Sun radiation forms the main source of energy intercepted by solar arrays. ™Rechargeable batteries are also included onboard SATs to ensure activity during darkness or a solar eclipse. 7) Atomic Clocks: ™Each SAT contains either 3 or 4 atomic clocks. Only one of the clocks is actively used; the others remain on standby in case of an emergency or during maintenance. 8) Operational SATs: ™As of November-200569 there are 29 operational SATs in outer-space based on 4 generations70.

66

Signal Freq is the rate of the data (binary); whereas the carrier Freq is the rate at which the data is transmitted from SAT to Rx. The 6 GPS orbitals are expected to be circular; however, they slightly tend to become elliptical due to a drift from the predefined position mainly caused by the gravitational pull of earth, moon and sun. This will eventually make the travel speed of SATs vary, and hence introduce position fix errors. GND control stations will reposition SATs periodically as will be explained later; also, some GPS-Rxs correct this factor using an offset rate value. 68 Period stands for the time it takes to go once around earth. 69 For the latest constellation information refer to: ftp://tycho.usno.navy.mil/pub/gps/gpsb2.txt ftp://tycho.usno.navy.mil/pub/gps/gpstd.txt and www.navcen.uscg.gov/ftp/gps/status.txt 70 In general new SAT will carry improved features while remaining backward compatible. 67

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SAT Generations Block-II Block-IIA Block-IIR Block-IIR-M

M. Abdulla

Number of SATs 1 15 12 1

Number of Active Clocks Cs Rb 1 0 8 7 0 12 0 1

Figure-6.22 Number of operational SATs and active Clocks w.r.t. GPS generations

9) Active SATs: ™At all times, 24 SATs must remain active to ensure a worldwide coverage. The remaining 5 SATs are there for backup in case an unexpected malfunction occurs or a deliberate shutdown is forced for maintenance. 10) Coverage Angle: ™SAT Field of View = 2 × 13.840 = 27.680 § 280

13.

84 0

25, 7 20

,3 5

0k

88 k m

m

Figure-6.23 Coverage angle of GPS SATs [K3-22]

11) Typical Maintenance required for each SAT:

™Atomic clocks need to have their beam-tube pumped. ¾Rate: Twice a year ¾Downtime: 18 hrs ™SATs need to be repositioned to their original predefined location using small onboard rocket boosters. ¾Rate: Once a year ¾Downtime: 12 hrs 93

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GPS-I Block-I

First Launch: Feb-1978 Last Launch: Oct-1985 Success: 10-SATs Failure: 1-SAT Clocks: 1-Cs , 2-Rb Solar Power: 410 watts Batteries: 3-15 cell NiCd Mass: 760 kg Design Life: 5 years MIL: P(Y) @ L1 , L2 By: Rockwell International [now Boeing]

GPS-II Block-II

Block-IIA

Block-IIR

Block-IIR-M

Block-IIF

First Launch: Feb-1989 Last Launch: Oct-1990 Success: 9-SATs Failure: None Clocks: 2-Cs , 2-Rb Solar Power: 710 watts Batteries: 3-15 cell NiCd Mass: 1660 kg Design Life: 7.5 years CIV: C/A @ L1 MIL: P(Y) @ L1 , L2 By: Rockwell International [now Boeing]

First Launch: Nov-1990 Last Launch: Nov-1997 Success: 19-SATs Failure: None Clocks: 2-Cs , 2-Rb Solar Power: 710 watts Batteries: 3-35 cell NiCd Mass: 1816 kg Design Life: 7.5 years CIV: C/A @ L1 MIL: P(Y) @ L1 , L2 By: Rockwell International [now Boeing]

First Launch: Jan-1997 Last Launch: Nov-2004 Success: 12-SATs Failure: 1-SAT Clocks: 3-Rb Solar Power: 1136 watts Batteries: 2-NiH2 Mass: 2032 kg Design Life: 10 years CIV: C/A @ L1 MIL: P(Y) @ L1 , L2 By: Lockheed Martin

First Launch: Sep-2005 Last Launch: -----------Success: 1-SAT [so far] Failure: None [so far] Clocks: 3-Rb Solar Power: 1136 watts Batteries: 2-NiH2 Mass: 2032 kg Design Life: 10 years CIV: C/A @ L1 L2C @ L2 MIL: P(Y) @ L1 , L2 M @ L1 , L2 By: Lockheed Martin

Expected Launch: 2007 Clocks: ???? Solar Power: 2440 watts Batteries: ???? Mass: 2900 kg Design Life: 15 years CIV: C/A @ L1 L2C @ L2 L5C @ L5 MIL: P(Y) @ L1 , L2 M @ L1 , L2 By: Boeing

GPS-III Block-III

NiCd: Nickel Cadmium NiH2: Nickel Hydrogen

Expected Launch: 2013 By: Boeing & Lockheed Martin

Figure-6.24 GPS generations [K5-4]

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D C

E Planes

F

B

A B C D E F

A

Main Slots Extra Slots 1 2 3 4 5 6 7 39 25 38 27 - - 56 30 44 35 - - 36 33 59 37 - - 24 46 45 34 15 53 61 51 47 40 54 - - 41 26 43 60 29 32 -

Numbers 15 and above represent the Satellite Vehicle Number (SNV) as of NOV-2005

Figure-6.25 GPS SAT Constellation71 left:[K6-25] right:[K6-26]

12) Each GPS SAT Transmit 3 Signals:

™Pseudo-Random Code (PRC)72: Contains SAT ID since each SAT has a unique PRC73. Also, the PRC is used to calculate the time it takes a signal to go from SAT to GPS-Rx; and therefore, it is often referred to as time signal. ™Ephemeris data: Contains SAT position w.r.t. time. ™Almanac data: Contains information about SAT status [healthy or unhealthy].

•

In the A/C: [a.k.a. User Segment] 1) Rx: GPS-Rx system. 2) Frequency: UHF

71

A list of all GPS SATs launched so far is available in Appendix F. The signal is called Pseudo-Random, because the bits (bits are binary since it either takes a 1 or a 0; also a bit is sometime called a chip and therefore the Freq of a digital signal is commonly referred to as chipping rate) appear as digital noise; however, this is not the case since the bit sequences do repeat after a specific time, and hence do carry useful information. 73 Even if signals are transmitted at the same frequency by different SATs, interference should not be an issue since each signal is unique due to its PRC. 72

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3) GPS-Rx will observe data form at least 4 SATs in order to solve for the unknowns using the 4-equations of (6.5). It is quite evident that an iterative numerical analysis approach will be used to solve for unknowns due to the nonlinearity of the equations. 4) The storage part of the Rx, which is updatable, contains a database with information on:

™Airspace ™Airports ™NAV facilities ™Etc. 5) The main purpose of GPS is to calculate A/C position fix; however, other secondary outputs are also made available such as:

™TAS & HDG ™GS & TK ™WS & WA ™Distance to next WPT and/or to destination ™ETA to next WPT and/or to destination ™Moving map display ™Intensity of each signal received ™Condition of each SAT tracked ™Etc.

Code Names

Processor

Signal from SAT

Control Interface Carrier Frequencies

Storage

Figure-6.26 GPS-Rx [K3-23]

•

Advantages: 1) 2) 3) 4) 5) 6) 7)

GPS is the most accurate NAV system ever invented. GPS provides continuous real-time NAV information. GPS is an all-weather system. GPS is available 24/7 to the international community. GPS is available free of charge without any subscription or license. Unlimited users could take advantage of GPS without degradation of the signals quality. For MIL activities, GPS could hit the target without causing major collateral damages.

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Disadvantages: 1) Errors:

Percentage of Occurance Accuracy 50 % 95 % Horizontal 4 m 9m

(i.e. LAT & LON)

Vertical (i.e. ALT)

10 m

22 m

Figure-6.27 Typical GPS errors [K3-24]

2) SAT Clock Errors: SATs use atomic clocks, and they are very precise; however sometimes discrepancies do happen and hence time measurement errors. 3) Orbital Errors: SATs should in general maintain their predefined orbital positions, however drifts do occur by gravitational pulls (earth, moon, sun).

4) Ionosphere and Troposphere Errors: As signals go from SAT to GPS-Rxs, they pass through the ionosphere and troposphere layers, and when this happens, the signal propagation speed (i.e. speed of light) is slowed down74. Note that the slowing rate is variant and non-constant; hence, correction or compensation for this factor is quite complicated. 5) Rx Noise Errors: The GPS-Rx will detect the desired NAV signals; however, the signal might be slightly distorted with noise due to the wireless nature of the system. 6) Multipath Errors: Ideally we want signals to go straight from SAT to GPS-Rx; however, on occasions the signals get bounced, and the Rx will detect these bounced signals.

Error GPS Errors Sources [m] SAT Clock 1.5 Orbital 2.5 Ionosphere 5.0 Troposphere 0.5 Rx Noise 0.3 Multipath 0.6 Total 10.4 Figure-6.28 GPS error sources [K6-27] 74

Speed of light remains constant only in vacuum (i.e. a space with no matter and very little gas pressure).

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7) Maintenance: The cost to maintain the GPS constellation annually, including R&D, is roughly $ 750,000,000 US. 8) Political Uncertainty: GPS program is managed by the DoD, which means that they may choose to selectively turn off GPS capabilities in certain geographical locations. •

Future: 1) Even though GPS is the most performant global NAV system, there is always place for improvement:

™Better accuracy ™Enhanced performance ™Added resistance to interference from noise ™Greater security for the MIL signals ™Etc. 2) It is expected that 2 to 4 SATs will be launched every year starting in 2006 to modernize the current SAT constellation. 3) More up-to-date GND stations are to be constructed in strategic locations to accommodate for GPS-III 75:

™New Monitor Stations ™A fully capable alternate Master Control Station located in California’s Vandenberg Air Force Base76. 4) The GPS market for CIV and commercial applications continues to grow exponentially as predicted by analyst:

™Observed in 2003: $ 16,000,000,000 US ™Forecasted by 2010: $ 68,000,000,000 US 5) GPS is doing well now and it must continue as such since important competition still exist or are about to emerge in the near future:

™Russian Federation: ¾Name: Global Navigation Satellite System (GLONASS) ¾Managed by: Russian Space Forces part of the Russian Ministry of Defense ¾First Launch: 1982 ¾Officially Operational: 1993-09-24 ¾Planes = 3 75 76

It is being said that GPS-III could achieve an accuracy of 1m or less. In the meantime until construction finishes, an interim backup Master Control Station exist near Washington D.C.

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¾Inclination = 1200 ¾Number of SATs per Plane = 8 ¾Number of Active SATs = 24 ¾SAT ALT = 19,100 km ¾Period = 11 hrs 15 min ™European Union (EU)77: ¾Name: GALILEO ¾Managed by: European Space Agency ¾Expected First Launch: 2006 ¾Expected Operations: 2008 ¾Planes = 3 ¾Inclination = 560 ¾Expected Number of SATs per Plane = 10 (9 active + 1 operational spare) ¾Expected Number of SATs = 30 (27 active + 3 operational spares) ¾SAT ALT = 23,616 km ¾Period = 14 hrs

GALILEO [EU]

GPS [US]

19,100 km

20,350 km

23,616 km

GLONASS [Russia]

Figure-6.29 GALILEO, GPS, and GLONASS SAT ALTs

77

Other Non-EU countries have joined the funding of the Galileo program such: Ukraine, Morocco, Saudi Arabia, Israel, India, and China. Countries that eventually might join the program are: Canada, Mexico, Brazil, Argentina, Chile, Norway, Pakistan, Malaysia, South Korea, Japan, and Australia.

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Chapter 7 Approach-Landing NAVAIDS

If you have knowledge, let others light their candle by it. — Margaret Fuller

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7.1 Basics of Approach-Landing – A/L •

A/L Information: Essentials required to achieve a successful A/L are: 1) Cockpit NAV Instruments 2) ATC data 3) Approach Charts: ™Hardcopy: i.e. on paper. ™Softcopy: i.e. on digital NAV Liquid Crystal Displays (LCDs).

A/L Phases: En-route control transfers responsibility to A/L control to assist in the following 3-phases:

(Horizontal NAV)

IAF

(Vertical NAV)

Top View

En-route Phase

Side View

•

IAF

Approach-Landing (A/L) Phases Transition

Final Approach

Visual

1

2

3

Runway

FAF

MDA DH

TDP

FAF MDA DH D

GS  3 Initial Approach Fix (IAF) Final Approach Fix (FAF) Minimum Descent Altitude (MDA) Decision Height (DH) Touchdown Point (TDP)

Runway

Instrument Landing System

Figure-7.1 A/L phases [K3-25]

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TDP

(ILS)

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1) Transition Phase: A/C leaves the En-route and enters into A/L. 2) Final Approach Phase78: A/C enters into the ILS Glideslope79 (GS0).

™IFR Precision Approaches: ¾Non-Precision: A/C does not support vertical NAV 80. ¾Precision: A/C does support vertical NAV. ™Depending on A/C type, decision must be taken at either MDA or DH on whether to: ¾Continue landing ¾Declare a missed approach and then decide to either: o Go around for another trial o Go to another airport

A/C

VFR

IFR

Decision @ MDA

Non-Precision

Precision

Decision @ MDA

Decision @ DH

Figure-7.2 MDA/DH decision tree

RVR [ft] [m] [ft] [m] I 200 60 1,800 550 II 100 30 1,200 365 III-A 50 15 700 210 III-B 0 50 0 15 150 45 III-C 0 0 0 0 CAT

DH

Runway Category (CAT) Runway Visibility Range (RVR)

Figure-7.3 ICAO DH values for IFR precision approaches [K6-28]

3) Visual Phase: From either MDA or DH until TDP, which roughly 1 km, NAV must be performed visually81. 78

To be more specific than what is shown on Figure-7.1, the final approach phase could end at either MDA or DH depending on the A/C flight rule and the precision used. 79 In this book GS refers to both Ground Speed (velocity) and Glideslope (angle); for the sake of differentiation, Glideslope acronym will be assigned as GS0 § 30. 80 In this case, as an example if ILS-GS0 is not available for landing support, other traditional vertical NAV tools are used such as: Altimeter and VSI as explained in Pages-31 & 32 respectively. 81 It is quite evident that for a VFR flight, visual NAV is used all along; however even for an IFR flight, the pilot (not the autopilot) must perform this phase visually until TDP.

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Visual A/L Aids: Visual runway support during A/L is quite useful for both VFR and IFR A/Cs. 1) Approach Lighting System – ALS

™Supported A/C: IFR-precision 82 ™Phases: DH until TDP ™Color Configurations: ¾DH ļ White ¾Pre-threshold Area ļ Red & White ¾Runway Threshold ļ Green ¾Centerline and Edges ļ White

e lan P tion a n li Inc

DH Pre-threshold Area Runway Threshold Centerline and Edges TDP

Figure-7.4 ALS [K3-26]

2) Visual Approach Slope Indicator System – VASIS

™Supported A/C: VFR and IFR-non-precision 82 ™Phases: MDA until TDP ™Color Configurations: ¾Too-high ļ White & White ¾Normal ļ Red & White ¾Too-low ļ Red & Red 82

Other type of A/C could still use this system.

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White White

Too High

Red White

Normal Approach

Red Red

Too Low Figure-7.5 VASIS [K6-29]

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Runway Numbering: Airport runways are numbered for identification. The method used to provide IDs are as follows: 1) Obtain the runway magnetic bearing from the approaching direction. 2) Rounded the bearing to the nearest 100. 3) Eliminate the last of the 3-digit bearing, the remaining 2-digits form the runway ID. 4) To obtain the bearing form the other runway extremity proceed as such:

Runway Bearing ­ Runway Bearing ½ ­ ½ 0 ® ¾ = ® ¾ ± 180 ¯ from one extremity ¿ ¯ from the other extremity ¿

(7.1)

5) Repeat steps 2 & 3 above to obtain the ID for the other extremity. 6) At large airports, there are parallel runways; hence, an extra letter is added to the ID to characterize the position: Left (L), Center (C) and Right (R). These parallel runways could either be double (i.e. 2-runways “L” & “R”) or triple (i.e. 3-runways “L” “C” “R”) 83.

2 0

0 2

0 9

2 7

Single-Runway

Other Runway Bearing ≈ 900 + 1800 = 2700 → ID : 27

Other Runway Bearing ≈ 200 + 1800 = 2000 → ID : 20

Double-Runways

Triple-Runways

Other Runway Bearing ≈ 2100 − 1800 = 300 = 0300 → ID : 03

2 0L 2 0C 2 0R

2 1L 2 1R

Runway Bearing = 2060 ≈ 2100 → ID : 21

0 2L 0 2C 0 2R

Runway Bearing = 180 ≈ 200 = 0200 → ID : 02

0 3L 0 3R

Runway Bearing = 930 ≈ 900 = 0900 → ID : 09

Runway Bearing = 2030 ≈ 2000 → ID : 20 Other Runway Bearing ≈ 2000 − 1800 = 200 = 0200 → ID : 02

Figure-7.6 Runway Numbering [K6-30] 83

The maximum possible number of runways in a specific direction cannot exceed 3.

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7.2 Instrument Landing System – ILS •

Principle: Provides A/C guidance for a straight flight path landing. ILS is used in IFR precision approach A/Cs from FAF until TDP. As for insuring an ideal landing, the system is based on the intersection of the runway centerline, the Localizer (LOC) beam, and the GS0 beam. T CLO

x Ru nw ay

Runway Centerline LOC (VHF) Horizontal Guidance

GS0-Tx

GS0 (UHF) Vertical Guidance

Figure-7.7 ILS [K3-27]

•

On the GND:

LOC-Plane

OM

ne 0 -Pla GS

DH Runway Threshold 1000 ft

200 ft

TDP

MM

IM 100 ft

FAF 1000 ft LOC-Tx

4 to 7 miles t

30 ft

0f 50

Transmissometer

3500 ± 250 ft

GS0-Tx

Figure-7.8 ILS CAT-II runway [K3-26]

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Outer Marker (OM) Middle Marker (MM) Inner Marker (IM)

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1) LOC–Tx ™Function: Provides alignment with runway centerline. ™NAV: Horizontal Guidance. ™Quantity per runway: 1 ™Location: At the end of the runway. ™Frequency: VHF § 108 – 112 MHz ¾Number of Channels: 20 ™Horizontal Range of Operation § 40 km ™Deviation from Centerline § ± 20 [i.e. 40]

40 km

LOC-Tx

Modulated @ 150 Hz

Strength @ 90Hz > Strength @ 150 Hz

Strength @ 90Hz < Strength @ 150 Hz

0

0

0

-2

+2

0

Modulated @ 90 Hz

40 Strength @ 90Hz = Strength @ 150 Hz Figure-7.9 ILS-LOC [K6-31]

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2) GS0–Tx ™Function: Provides fix descent rate. ™NAV: Vertical Guidance. ™Quantity per runway: 1 ™Location: On the side of the runway. ™Frequency: UHF § 329 – 335 MHz ¾Number of Channels: 20 ™Vertical Range of Operation § 1 km ™Typical GS0 Inclination § 30 ™Deviation from GS0 § ± 0.70 [i.e. 1.40]

Strength @ 90Hz = Strength @ 150 Hz

1 km

1.40

3.7

3

0

2.3

0

Modulated @ 90 Hz

0

Strength @ 90Hz > Strength @ 150 Hz

GS0-Tx

Modulated @ 150 Hz Strength @ 90Hz < Strength @ 150 Hz

Figure-7.10 ILS-GS0 [K6-31]

3) MB–Tx84 ™Function: Provides indication to crew that the A/C is in a specific location. ™NAV: Horizontal Guidance. ™Quantity per runway: 2 or 3 85 ™Location: Prior to runway along its centerline. ™Frequency: VHF § 75 MHz 84

NDB (Non-Directional Beacon) and MB (Marker Beacon) differ in the sense that NDB transmit signals in all directions, whereas MB emits in the upward direction only. 85 All runway CATs have 3 MBs (OM, MM and IM) except CAT-I contains only 2 MBs (OM and MM).

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GS0-Tx

LOC-Tx

MB-Tx

Figure-7.11 LOC, GS0, and MB-Txs [K5-5]

4) Transmissometer: System used to measure the transmission of light through the atmosphere in order to determine visibility, and hence RVR. ™Function: System used to measure the transmission of light through the atmosphere in order to determine visibility, and hence RVR. ™Quantity per runway: 2 ™Location: On the side of the runway. ™Range of Operation § 10 km ™The system is able to identify 7 different types of pricipitation: ¾Drizzle (i.e. gentle rain) || Rain ¾Frizzing Drizzle || Freezing Rain ¾Mixed Rain & Snow ¾Snow || Ice pellets

Figure-7.12 Transmissometer [K4-11]

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In the A/C: 1) LOC/GS0–Rx or HSI–System86 ™Frequency: ¾VHF: LOC ¾UHF: GS0 ™Rx compares the strength of the 90 and 150 Hz modulated signals for both LOC and GS0, and outputs the actual A/C position w.r.t. ideal centered path.

90 Hz Filter Compare Strength

Rx

Comparing Circuit

LOC (VHF) GS0 (UHF)

150 Hz Filter

LOC/GS0 Indicators

Figure-7.13 LOC/GS0-Rx [K3-28]

2) MB–Rx ™Frequency: VHF ™Rx detected the signal sent by the GND MB-Tx and alerts the A/C crew audibly and visually.

Audio Output

Rx

OM

MM

IM

400 Hz Filter

1,300 Hz Filter

3,000 Hz Filter

Blue

Amber

White

Audible Alerts Visual Alerts Tone Freq Morse Code Color Continuous: OM 400 Hz Blue Alternate: & MM 1,300 Hz Amber Continuous: IM 3,000 Hz White MB

Figure-7.14 MB-Rx and its alerts left:[K3-29] right:[K6-28] 86

For more on HSI refer to pages-68 & 69.

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•

Advantage: ILS is a powerful system available for landing guidance.

•

Disadvantages: 1) LOC and GS0 signals suffer from bending due to site and terrain effect.

Ideal Signal Path Actual Signal Path LOC or GS0-Tx

Figure-7.15 Terrain effect in ILS [K3-30]

2) GS0 signals are highly sensitive w.r.t. LOC; and therefore, they are also affected by:

™Snow ™Airport GND moisture ™Airport GND vehicle movement 3) The path used for landing in ILS cannot be flexible; it must remain straight at all times. 4) Only 20 frequency channels are available for LOC and GS0 use. 5) High cost of installation and maintenance. •

Future: ILS is expected activity until 2010 in most A/Cs and airports; following that, it will remain available as a backup system in case an unexpected malfunction occurs to GPS and/or DGPS.

7.3 Microwave Landing System – MLS •

Principle: Provides A/C guidance for curved or straight or segmented flight path landing. The main outputs obtained using MLS are bearing, slant distance87, and ALT in the approach terminal area. Also it is important to mention the MLS system is exclusively used by MIL88 due to its flexibility in A/L as opposed to the CIV ILS.

87

Usually a DME system (UHF) is integrated within the Azimuth-Tx (SHF), and hence the slant distance w.r.t. it is also available. Even tough MLS is a MIL system, some EU countries, due to visibility conditions, have obtained license for commercial use to operate them as an alternative for ILS.

88

111

M. Abdulla +1 50

1.5 km

0

0 +2

13

Runway

20 0

Chapter 7: Approach-Landing NAVAIDS

0

+1

km

A/L missed or Departure

A/L 15 0

m

+400

+1

0

til

l+

k 37

0

0 +4

40 0

0

+1 0

6 km

5 +1

Curved Path

Straight Path

Segmented Path

Figure-7.16 MLS [K6-32]

•

On the GND: 1) Azimuth–Tx ™Function: Provides bearing information. ™NAV: Horizontal Guidance. ™Quantity per runway: 2 ™Location: One is placed at the end of the runway, and the other one at the begging 89. ™Frequency: SHF § 5.031 – 5.0907 GHz ¾Number of Channels: 200 ™Horizontal Range of Operation § 37 km ™Deviation from Centerline § ± 400 [i.e. 800] 90

89

The one located at the end of the runway is used for approaching A/Cs, whereas the one located at the front of the runway is used for either missed approaches or for departure NAV. 90 MLS horizontal guidance has a coverage area 20-times that of ILS (20 × 40 = 800).

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2) Elevation–Tx ™Function: Provides ALT information. ™NAV: Vertical Guidance. ™Quantity per runway: 1 ™Location: On the side of the runway. ™Frequency: SHF § 5.031 – 5.0907 GHz 91 ¾Number of Channels: 200 ™Vertical Range of Operation § 6 km ™Typical MLS Inclination § 80 ™Deviation from MLS § ± 70 [i.e. 140] 92

A/L Azimuth-Tx

Back Azimuth-Tx

Elevation-Tx

Figure-7.17 Configuration of MLS GND systems [K6-33]

Elevation-Tx

Azimuth-Tx

Figure-7.18 Azimuth and Elevation-Txs [K5-6] 91

Even though Azimuth and Elevation-Txs transmit at the same frequency, there is no critical signal interference among them due to timeshared operations. 92 MLS vertical guidance has a coverage area 10-times that of ILS (10 × 1.40 = 140).

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In the A/C: 1) Rx: MLS-Rx system. 2) Frequency: SHF 3) Primary outputs from MLS: ™Bearing / Slant Distance ™ALT 4) Secondary outputs from MLS: ™Meteorological info ™Runway Status ™Etc.

•

Advantages: 1) 2) 3) 4) 5) 6)

Improved guidance accuracy with greater coverage area. Provide flexible landing path NAV. Offers guidance for missed approaches and departure NAV. MLS has low sensitivity from weather conditions and airport GNS traffic as oppose to ILS. MLS offers 200 frequency channels, 10-times more than ILS. Low cost of installation and maintenance.

•

Disadvantage: The use of MLS is not quite spread among CIV A/Cs.

•

Future: Similar to ILS, MLS is expected to be phased-out around 2010 due to GPS and DGPS improved accuracy.

7.4 Differential Global Positioning System – DGPS •

Principle: GND system used to increase GPS accuracy. In fact, DGPS is typically found in airports in order to bring a more precise A/C position fix during the A/L phases. As for the A/C, it must be equipped with a GPS-Rx so that signals from both SAT and DGPS would be observed to correct position errors.

Figure-7.19 DGPS [K4-12]

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F UH F UH

UH

UHF

F UH

DGPS

UH UH F F

F UH F

LF/M

F

Calculated A/C Position = {XA/C , YA/C , ZA/C}

Actual DGPS Position = {XD0 , YD0 , ZD0} Calculated DGPS Position = {XD , YD , ZD}

Figure-7.20 DGPS used to correct A/C position fix [K6-34]

•

On the GND: 1) Rx-Tx: DGPS system. 2) Frequency: ™Rx: UHF [used to calculate DGPS position fix] ™Tx: LF/MF § 283.5 – 325 kHz [used to transmit correction signal to A/C] 3) The DGPS is stationary, therefore its actual {LATD0, LOND0, ALTD0}93 is well known. Then we could use Equation-6.7 to transform it to {XD0, YD0, ZD0}. 4) Similar to what was seen in the GPS section of Chapter-6, we would use 4-SATs to obtain a 3D position fix for the DGPS. This calculated position is identified as {XD, YD, ZD}. 5) The DGPS then takes the difference that exists between the actual known position and the calculated position obtained using GPS SATs.

∆ = Calculated Position − Actual Position Calculated DGPS Position

∆=

93

§ XD · ¨ ¸ ¨ YD ¸ ¨Z ¸ © D¹

(7.2)

Actual DGPS Position

§ X D0 · ¨ ¸ − ¨ YD 0 ¸ ¨Z ¸ © D0 ¹

(7.3)

Even if DGPS is located on the GND, it still has a height for its antenna and therefore, we consider a 3D = {LAT, LON, ALT} position rather than a 2D = {LAT, LON} position.

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6) Ideally, ¨ should be roughly zero; however, most of the time this is not the case, and therefore the ¨ information is transmitted to the airborne GPS-Rx in the form of a correction signal. •

In the A/C: 1) Rx: GPS-Rx system. 2) Frequency: ™Rx: UHF [used to calculate A/C position fix] ™Rx: LF/MF [used to observe correction signal from DGPS] 3) Range of Operation § 370 km 94 4) Again, the A/C obtains its 3D position fix using the 4-SATs. 5) Then, the GPS-Rx detects the correction signal that contains the ¨ information and performs the following correction:

Actual Position = Calculated Position − ∆

(7.4)

Calculated A/C Position

§ X A /C ¨ Actual A / C Position = ¨ Y A / C ¨Z © A /C •

· ¸ ¸ −∆ ¸ ¹

Advantages: 1) GPS is quite accurate; however, using DGPS pushes its accuracy even further. 2) GPS/DGPS makes A/L guidance every precise as oppose to ILS and MLS.

•

Disadvantages: 1) Errors:

Accuracy

Errors [m]

Horizontal

1.3

(i.e. LAT & LON)

Vertical (i.e. ALT)

2

Figure-7.21 Typical DGPS errors [K3-31]

94

In other words, the maximum distance that separates the GND DGPS and the airborne GPS-Rx cannot exceed 370 km.

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2) Most of the errors are either completely eliminated or made negligible after using DGPS; however, atmospheric (i.e. Ionosphere & Troposphere) and Rx-based (i.e. Rx-Noise & Multipath) errors would still exist.

Error DGPS Errors Sources [m] SAT Clocks 0.0 Orbital Error 0.0 Ionosphere 0.4 Troposphere 0.2 Rx Noise 0.3 Multipath 0.6 Total 1.5 Figure-7.22 DGPS error sources [K6-27]

3) The coverage area to take advantage of DGPS is limited. 4) To ensure greater coverage area more DGPS stations need to be added. 5) The position accuracy degrades as the separation between DGPS and A/C GPS-Rx increases. •

Future: 1) Currently there are 84-DGPS stations in the US95. 44 more DGPS sites are expected to be added in the next 15-years. 2) Likewise, in Canadian territories there exist 19-DGPS stations96. Addition of more stations is expected in the near future. 3) There are also systems that exist today and have promising future that are based on DGPS such as:

™Wide Area Augmentation System (WAAS): It is based on 25-GND stations spread strategically across the US. Similar to DGPS the difference between the actual position and the calculated position using GPS SATs is obtained for each of the stations. Then their data are sent to the WAAS Master Station (WMS) to be compiled; once this is done, a correction 95 96

For present US DGPS status refer to: www.navcen.uscg.gov/ado/DgpsCompleteConfiguration_tabular.asp For present Canadian DGPS status refer to: Atlantic Cost www.ccg-gcc.gc.ca/dgps/dgpsatlantic_e.htm Pacific Coast www.ccg-gcc.gc.ca/dgps/dgpspac_e.htm Great Lakes and St. Lawrence River www.ccg-gcc.gc.ca/dgps/dgpscen_e.htm

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M. Abdulla signal is directed to WAAS SATs 97, which in turn transmit the signal to GPS-Rxs for position correction.

™Local Area Augmentation System (LAAS): This system is very similar to WAAS but on a much smaller scale98. Again here, GND stations are located at known positions across the airport, then a calculated position fix is obtained for each of these stations and the offset is measured. Once this is done, offsets from each station are sent to the airport central location for compilation purposes. Finally, the correction signal is sent from the central location to airborne GPS-Rxs.

97 98

WAAS SATs are not GPS SATs; they are specifically used to transmit the correction signal to GPS-Rxs. WAAS is based on a large network across the US; whereas LAAS is a network used within an airport. That is, each airport contains its own LAAS system for guidance in the precision A/L phase. It is also interesting to note that both of these systems are developed and maintained by the FAA.

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There is no substitute for hard work. — Thomas Edison

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8.1 Nomenclature 2D 3D A/C AFIS A/L ATC ELT GND HF IFR LF MF MIL NAV NAVAIDS

Latitude and Longitude Latitude, Longitude, and Altitude Aircraft Airborne Flight Information System Approach Landing Air Traffic Control Emergency Locator Transmitter Ground High Frequency Instrument Flight Rule Low Frequency Medium Frequency Military System Navigation Navigational Aids

OS P/O RA Rx SATCOM SHF TCAS Tx UHF VFR VHF VLF WPT W.R.T. WXR

Outer-Space Phased-Out systems Radio Altimeter Receiver Satellite Communications Super High Frequency Traffic-Alert and Collision Avoidance System Transmitter Ultra High Frequency Visual Flight Rule Very High Frequency Very Low Frequency Waypoint With Respect To Weather Radar System

8.2 Summary of Avionic Systems MEANING

PRINCIPLE

FREQUENCY

ADF

Automatic Direction Finder

MF

NDB

Non-Directional Beacon

Provides A/C bearing w.r.t. a GND station GND system used as an ADF Tx for bearing purposes

VOR

VHF Omni-directional Range

Provides A/C radial w.r.t. a GND station

SYSTEM LOCATION GND A/C OS

CHART SYMBOL

MF VHF

Provides distance between A/C and GND station GND system with both NDB and DME for NDB-DME NDB & DME bearing and distance purposes GND system with both VOR and DME for VOR-DME VOR & DME radial and distance purposes Provides A/C bearing TACtical Air and distance w.r.t. a TACAN Navigation GND station GND system with both VOR and TACAN for VORTAC VOR & TACAN bearing and distance purposes Provides A/C bearing Random NAVigation and distance w.r.t. 3D or RNAV artificial reference aRea NAVigation position known as WPT

DME

Continental NAV

Short-Range NAVAIDS

RANGE SYSTEM

Distance Measuring Equipment

UHF

MF / UHF

VHF / UHF

UHF

VHF / UHF VHF / UHF SHF

Figure-8.1 Short-Range Avionics

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Fly-By Fly-Over

MIL P/O

Chapter 8: Summary

LORAN-C

Intercontinental NAV

Long-Range NAVAIDS

RANGE SYSTEM

OMEGA

M. Abdulla

MEANING

PRINCIPLE

FREQUENCY

LOng RAnge Provides A/C position Navigation fix (2D) (revision-C) Optimized Method for Provides A/C position Estimated Guidance fix (2D) Accuracy

SYSTEM LOCATION GND A/C OS

CHART SYMBOL

MIL P/O

SYSTEM LOCATION GND A/C OS

CHART SYMBOL

MIL P/O

LF

VLF

INS or IRS

Inertial Navigation or Reference System

Provides A/C velocity (3D) and position fix (3D)

------

DNS

Doppler Navigation System

Provides A/C velocity (3D) and position fix (3D)

SHF

GPS

Global Positioning System

Provides A/C position fix (3D)

UHF

Figure-8.2 Long-Range Avionics

RANGE

8.4

SYSTEM

MEANING

PRINCIPLE

FREQUENCY

Provides visual aid Approach Lighting during landing for ALS Approach-Landing NAVAIDS System IFR-precision A/C

------

Provides visual aid

Terminal-Area NAV

Approach-Landing NAVAIDS

VASIS

Visual Approach Slope during landing for VFR and IFR-non-precision Indicator System

ILS

Instrument Landing System

LOC

LOCalizer

GS0

GlideSlope

LOC-DME

LOC & DME

MB

Marker Beacon

OM MM IM

Outer Marker Middle Marker Inner Marker

MLS

Microwave Landing System

DGPS

Differential GPS

A/C Provides A/C guidance for straight flight path landing Provides horizontal guidance during ILS landing Provides vertical guidance during ILS landing GND system with both LOC and DME for horizontal guidance during ILS landing and distance purposes Provides indication that the A/C is in a specific location Provides indication on how far the A/C is w.r.t. the runway threshold Provides A/C guidance for curved or straight or segmented flight path landing GND system used to increase GPS accuracy

------

VHF / UHF VHF UHF

VHF / UHF

VHF VHF

SHF LF / MF UHF

Figure-8.3 A/L Avionics

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8.3 Avionic Receivers and/or Transmitters

RANGE SYSTEM

NDB

Continental

Short-Range

ADF

VOR DME TACAN

Terminal-Area Intercontinental

A/L Phase Long-Range

VORTAC LORAN-C OMEGA DNS GPS ILS MB MLS DGPS

On the GND In the A/C Tx Rx Tx Rx

In Space Tx Rx

--- --- ------- --- --- ----- ----------- --- ----- ------- ------- --------- ------- ------- ------- --- ---

Figure-8.4 Avionic Rxs and/or Txs

8.4 Airborne Antennas Short-Range NAVAIDS Long-Range NAVAIDS A/L NAVAIDS Short-Range & A/L NAVAIDS Other Figure-8.5 Color coding used to classify avionics

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HF-Antenna

(Rx / UHF)

(Rx and/or Tx)

VHF-Antenna (Rx and/or Tx)

ELT (Tx / VHF)

UHF-Antenna (Rx and/or Tx)

AFIS (Rx-Tx / VHF)

VOR & ILS-LOC (Rx / VHF)

ATC (Rx-Tx / VHF)

TCAS (Rx-Tx / UHF)

GPS (Rx / UHF)

ILS-LOC (Rx / VHF)

ILS-GS0 (Rx / UHF)

WXR

MLS

TACAN

ADF

(Rx / SHF)

(Rx-Tx / UHF)

(Rx / MF)

(Rx-Tx / SHF)

Figure-8.6 Top-view of airborne avionics [K2-2]

Avionics Bay TCAS (Rx-Tx / UHF)

ATC (Rx-Tx / VHF)

ILS-GS0

MLS

(Rx / UHF)

(Rx / SHF)

VHF-Antenna

UHF-Antenna (Rx and/or Tx)

MB

DME

DNS

RA

ADF

(Rx / VHF)

(Rx-Tx / UHF)

(Rx-Tx / SHF)

(Rx-Tx / SHF)

(Rx / MF)

Figure-8.7 Bottom-view of airborne avionics [K2-2]

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(Rx and/or Tx)

Appendices Appendix A: Matlab code that transforms LAT or LON from hour/minute/second to decimal format %HMS_TO_DECIMAL Transforms latitude or longitude from % hour/minute/second format to a decimal degree format % %DEC = HMS_TO_DECIMAL(HH,MM,SS,'DIRECTION') % %'DIRECTION' could take 4 type of inputs (case sensitive/ must be in CAPS): % 'N' - for North -> Latitude will be + % 'S' - for South -> Latitude will be % 'E' - for East -> Longitude will be + % 'W' - for West -> Longitude will be % %HH - refers to hours or degrees -> If 'N' or 'S' is used HH possible set = {0 , 90} % -> If 'E' or 'W' is used HH possible set = {0 , 180} % %MM - refers to minutes -> MM possible set = {0 , 60} % %SS - refers to seconds -> SS possible set = (0 , 60} % %DEC - refers to degrees in decimal format % %Example: Montréal/QC/Canada LAT: 45deg 30min 0sec North || LON: 73deg 35min 0sec West % LAT_DEC = HMS_TO_DECIMAL(45,30,0,'N') -> LAT_DEC = 45.5000 % LON_DEC = HMS_TO_DECIMAL(73,35,0,'W') -> LON_DEC = - 73.5833 % %See also DECIMAL_TO_HMS. %Mouhamed Abdulla, October 2005 function dec = hms_to_decimal(hh,mm,ss,di) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Validating Inputs%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if((di~='N') & (di~='S') & (di~='E') & (di~='W')) error('Invalid "direction" entered! Valid values are N or S or E or W, and they must be in CAPS!') end if((di=='N') | (di=='S')) if((hh90)) error('Invalid "hours" or "degrees" entered! Value must be within "0" to "90" inclusive.') end end if((di=='E') | (di=='W')) if((hh180)) error('Invalid "hours" or "degrees" entered! Value must be within "0" to "90" inclusive.') end end if((mm60)) error('Invalid "minutes" entered! Value must be within "0" to "60" inclusive.') end if((ss60)) error('Invalid "seconds" entered! Value must be within "0" to "60" inclusive.') end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Transformation%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if((di=='N') | (di=='E')) sign = 1; else sign = -1; end temp = (((ss/60) + mm) / 60) + hh; dec = sign * temp;

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Appendix B: Matlab code that transforms LAT or LON from decimal to hour/minute/second format %DECIMAL_TO_HMS Transforms latitude or longitude from decimal degree format % to hour/minute/second format % %[HH,MM,SS,'DIRECTION'] = DECIMAL_TO_HMS(DEC,'X') % %'X' could take 2 type of inputs (case sensitive/ must be in CAPS): 'LAT' - for % 'LON' - for % %DEC - refers to degrees in decimal format -> If 'LAT' is used DEC possible set % -> If 'LON' is used DEC possible set % %HH - refers to hours or degrees % %MM - refers to minutes % %SS - refers to seconds % %'DIRECTION' could refer to either: 'N' - for North % 'S' - for South % 'E' - for East % 'W' - for West % %Example: Montréal/QC/Canada LAT: 45.5000 || LON: -73.5833 % [H1,M1,S1,D1] = DECIMAL_TO_HMS( 45.5000,'LAT') -> H1 = 45 | M1 = 30 | % [H2,M2,S2,D2] = DECIMAL_TO_HMS(-73.5833,'LON') -> H2 = 73 | M2 = 34 | % % %See also HMS_TO_DECIMAL. %Mouhamed Abdulla, October 2005

Latitude Longitude = {-90 , 90} = {-180 , 180}

S1 = 0 | D1 = N S2 = 59.8800| D2 = W

function [hh,mm,ss,di] = decimal_to_hms(dec,x) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Validating Inputs%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if(~strcmp(x,'LAT') & ~strcmp(x,'LON')) error('Invalid "X" entered! Valid values are LAT or LON, and they must be in CAPS!') return end if(x=='LAT') if((dec90)) error('Invalid "degrees" entered! Value of LAT must be within "-90" to "90" inclusive.') end end if(x=='LON') if((dec180)) error('Invalid "degrees" entered! Value of LON must be within "-180" to "180" inclusive.') end end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Transformation%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% s = sign(dec); if(x=='LAT') if(s==0 | s==1) di = 'N'; else di = 'S'; end end if(x=='LON') if(s==0 | s==1) di = 'E'; else di = 'W'; end end

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%FIX is a Matlab function that ignores any decimal and keeps the integer part only. d = abs(dec); hh = fix(d); t1 = (d - hh) * 60; mm = fix(t1); t2 = t1 - mm; ss = (t2 *60); %We could round the result here to get an integer "seconds" value, %or we could leave the way it is for the sake of greater accuracy.

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Appendix C: ALT, Temperature, Pressure w.r.t. the Atmosphere

Outer Space

Appendices

20,350 km GPS Satellite

10,000 km

700 km

↑ ALT

& ↑ Temp & ↓ Air Molecules

300 km

Ionosphere Layer

In this region temperature increases with an increase in altitude; however, our human skin will still freeze since air molecules are less, and hence less energy is transferred to our skin.

85 km

↑ ALT

& ↓ Temp & ↓ Air Molecules 60 km 50 km

↑ ALT

& ↑ Temp & ↓ Air Molecules 15 km

↑ ALT

&

↓ Temp

&

↓ Air Molecules

Figure-C.1 Atmosphere layers [K5-7]

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0 km

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Figure-C.2 ALT as a function of temperature [K5-8]

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Maximum ALT for a B747-400 = 40,000 ft = 12.2 km

Highest peak in North America located in Alaska

Figure-C.3 ALT as a function of pressure [K5-9]

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Appendix D: Matlab code that transforms {X,Y,Z} to {LAT,LON,ALT} %XYZ_TO_LLA Transforms Earth Centered Earth Fixed (ECEF) Cartesian system (X,Y,Z) % to geodetic system (LAT,LON,ALT) % %[LAT,LON,ALT] = XYZ_TO_LLA(X,Y,Z) % %X Y Z - refers to the ECEF coordinates in "meters" % %LAT - refers to latitude in "degrees". % %LON - refers to longitude in "degrees". % %ALT - refers to altitude in "meters". % %Example: X: 1109900 [m] || Y: -4860100 [m] || Z: 3965200 [m] % [LAT,LON,ALT] = XYZ_TO_LLA(1109900,-4860100,3965200) -> LAT = 38.6860 | LON = -77.1360 | ALT = 46.4497 % %See also LLA_TO_XYZ. %Mouhamed Abdulla, October 2005 function [lat,lon,alt] = xyz_to_lla(x,y,z) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Transformation%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% a = 6378137; %Earth equatorial radius b = 6356752.3142; %Earth polar radius f = (a-b)/a; %Flattening of ellipsoid e2 = f*(2-f); %First eccentricity of ellipsoid squared ep2 = (a^2 - b^2) / b^2; %Second eccentricity of ellipsoid squared p = sqrt(x^2 + y^2); th = atan((z*a)/(p*b)); t1 = z + ep2 * b * (sin(th))^3; t2 = p - e2 * a * (cos(th))^3; latr = atan(t1/t2); %LAT in radians lonr = atan2(y,x); %LON in radians lat = (180/pi)*latr; %LAT in degrees lon = (180/pi)*lonr; %LON in degrees v = a / sqrt(1 - (e2*(sin(latr))^2)); %Radius of curvature alt = (p/cos(latr)) - v; %ALT in meters

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Appendix E: Matlab code that transforms {LAT,LON,ALT} to {X,Y,Z} %LLA_TO_XYZ Transforms geodetic system (LAT,LON,ALT) to % Earth Centered Earth Fixed (ECEF) Cartesian system (X,Y,Z). % %[X,Y,Z] = LLA_TO_XYZ(LAT,LON,ALT) % %LAT - refers to latitude in "degrees" with possible set = {-90 , 90} % %LON - refers to longitude in "degrees" with possible set = {-180 , 180} % %ALT - refers to altitude in "meters" with possible set = {0, ALT>0} % %X Y Z - refers to the ECEF coordinates in "meters" % %Example: LAT: 38.6858 [deg] || LON: -77.1357 [deg] || ALT: 25 [m] % [X,Y,Z] = LLA_TO_XYZ(38.6858,-77.1357,25) -> X = 1.1099e+006 | Y = -4.8601e+006 | Z = 3.9652e+006 % %See also XYZ_TO_LLA. %Mouhamed Abdulla, October 2005 function [x,y,z] = lla_to_xyz(lat,lon,alt) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Validating Inputs%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if((lat90)) error('Invalid "degrees" entered! Value of LAT must be within "-90" to "90" inclusive.') end if((lon180)) error('Invalid "degrees" entered! Value of LON must be within "-180" to "180" inclusive.') end if(alt